Search for the best MSSP in London and you get three directories, a handful of providers who built a page for that exact phrase, and almost no way to tell them apart. Every one of them claims 24/7 monitoring, rapid response and expert analysts. None of those claims is checkable from the page you are reading.
Transputec is one of the providers in that search, so read this as a document written by an interested party. We have been a London-headquartered managed service provider for 40 years, we are still independent rather than private equity owned, and we run six cyber security services behind one accountable UK SOC. Those are exactly the sort of claims you should make a provider evidence, which is the point of everything below.
So this is not another list. It is what to ask, what the answers should sound like, and which questions actually separate one provider from another. Transputec’s own answers are in here, in the same format as everybody else’s, so you can mark us against the same criteria instead of taking our word for anything.
The NCSC has already published the shortlist criteria, and almost nobody selling to you cites them. Start there, not with a vendor’s own comparison table, Transputec’s included.
What an MSSP Does, and Where It Stops
A managed security service provider runs security operations on your behalf: monitoring, detection, triage and, depending on the contract, response. An MSP runs your IT. The two overlap and plenty of firms do both, but they are bought for different reasons and judged on different things.
The distinction matters when you are choosing an MSSP in London, because the market here contains all three of these and they price very differently:
| Type | What you are buying | Judge it on |
|---|---|---|
| MSP | Day-to-day IT: devices, service desk, infrastructure | Ticket resolution, uptime, user satisfaction |
| MSSP | Security monitoring and detection across your estate | What it catches, how fast, and who acts on it |
| MDR | Detection plus active response, usually on endpoints | Containment time and what they are authorised to do |
The question that cuts through most sales conversations is simple. When something is detected at three in the morning, who actually does something about it, and what are they allowed to do without ringing you first? A provider selling monitoring will tell you they alert you. A provider selling response will tell you what they contain on their own authority. Those are different products at different prices, and the brochures for both say “24/7”.
Transputec sells both rows, deliberately and separately. The managed SOC is the monitoring and detection line, and managed detection and response is the one that adds containment. Which of the two your estate actually needs is a conversation worth having before anyone quotes, and it is the first thing we try to settle rather than the last.
Transputec has written the longer comparison in managed SOC versus managed SIEM, which covers the same confusion one layer down: the platform is not the service, and buying the platform without the people is the most common expensive mistake in this category.
What the Directories Ranking for This Search Will Not Tell You
Several of the results for this search are aggregator listings. They are useful for building a longlist and useless for ranking one, and it is worth understanding why before you take their order seriously.
Directory rankings are typically built from profile completeness, review counts and recency of activity. One of the lists returned for this phrase publishes its own weighting: reputation and trust, profile quality, and freshness. Nothing in that formula measures whether a provider detected anything, how fast they escalated it, or whether the analyst who picked up the phone had seen your kind of estate before.
That is not a criticism of the directories. They are doing lead generation and they are open about the method. It is a warning against treating position on those lists as a quality signal, which is exactly how they tend to get read. If you are shortlisting an MSSP in London, use them to assemble names and nothing beyond that.
The same caution applies to the vendor pages that rank, including this one. Transputec turns up on some of those directory lists too, and where we sit on them tells you nothing useful either way. A page can be written to match a search phrase without the service behind it being any different. Everything below is designed to be checkable on a call, because that is the only place the differences show up.
Want to Skip the Shortlist and Put the Hard Questions to Transputec?
Every question in this article is one we expect to be asked. Book an initial security consultation with a Transputec security architect and put them to us directly.
Book a consultationThe NCSC Has Already Written Your Shortlist Criteria
This is the part most buyers miss. The NCSC publishes a guide called Choosing a managed service provider (MSP), published on 24 November 2025. It is short, free, vendor-neutral, and it is a better basis for assessing an MSSP in London than any comparison table a provider will hand you.
On certifications it is direct:
You should use MSPs with recognised certifications such as Cyber Essentials Plus. Other certifications like ISO 27001 or SOC 2 demonstrate an organisation takes information security seriously.
On contracts, three requirements worth lifting straight into your tender document. Specify how incidents will be reported, “including whether the MSP will notify you if they experience one”. Ensure “there is clear agreement on who is accountable for vulnerabilities, damages, and incident impacts”. And insist on “clear, detailed contracts that specify responsibilities, response times, and liability”, including “responsibility for any third parties your MSP uses to deliver the service”.
That last clause is the one providers dislike most and the one you should hold firmest. Plenty of security services are delivered partly by somebody else’s platform or somebody else’s night shift. If the contract does not reach them, your recourse stops at your supplier’s front door.
The word Transputec uses for its own position on that clause is accountable: six cyber security services behind one accountable UK SOC, which is a claim about where responsibility lands rather than a claim about tooling. It is also a claim you should test with the NCSC’s third-party wording above, on us first and then on everyone else you shortlist.
On access, the guidance is equally blunt: use “least privilege (giving your MSP only the permissions needed to do the job)”, and “check that MSPs also protect their access to your systems”. A provider that asks for standing global administrator rights on day one has answered an important question about itself.
On patching it sets a number: “Our recommendation is that software is patched within 14 days of an update being released”. The same 14 days appears in the Cyber Essentials requirements for IT infrastructure, so it is worth writing into the service description rather than leaving to good intentions.
Where Your Analysts Actually Sit
This is the question that separates providers fastest, and it is the one most often answered with a dodge.
“UK-based” can mean the company is registered here. “24/7” can mean a rota covered from several countries, which is a perfectly reasonable model and not something to be squeamish about, as long as you know. What you are entitled to ask any MSSP in London is plainer than that:
Where do the analysts on the overnight shift physically sit, and are they employed by you or by a partner?
Is the person who triages my alert at 3am the same organisation I signed a contract with?
If my data is monitored, where is it stored and processed, and does that create an obligation I do not currently have?
None of those have a wrong answer. An offshore follow-the-sun model can be excellent and is often faster, because somebody is always mid-shift rather than being woken up. A single-site UK team can be excellent for different reasons. What matters is that the answer is specific, volunteered, and matches what the contract says.
For the record on ours: Transputec’s service desk and Security Operations Centre are headquartered in London, in Wembley, and “Where are your SOC analysts based?” is a question we answer on the cyber security services page rather than leaving for the call. The point is not that London is the right answer. It is that you should get a straight one.
One related question that belongs on more shortlists than it appears on: who owns the provider. Transputec is 40 years old, founded in 1986, with more than 120 specialists, and still independent rather than private equity owned. That has little bearing on who answers at 3am tonight and a great deal on whether the team you met is the team you have in two years. In a market consolidating as fast as this one, it is a fair thing to ask anybody, and the why partner page is where our answer sits.
Ask What Happens on the Worst Day, Not the Average One
Most evaluations of an MSSP in London test the steady state: dashboards, reporting, how many alerts a month. The steady state is not what you are buying insurance against.
Four questions about the bad day, and what a good answer sounds like.
What is your response time, and response to what? A fifteen-minute SLA on acknowledging an alert is not the same as a fifteen-minute SLA on beginning containment. Ask which one is in the contract, and what the remedy is when it is missed. If the remedy is a service credit worth a fraction of a day’s downtime, the SLA is a comfort blanket.
What are you authorised to do without me? Isolating a host, disabling an account, blocking a domain. Each one has a business cost if they get it wrong, which is why many providers will not do any of them unilaterally. That is a legitimate position, but it means your people are still the response team and you should staff accordingly.
What happens when the incident is bigger than the service? Monitoring contracts routinely exclude full incident response, forensics and recovery. Find out what the day rate is and whether you have a retainer before you need one, because the pricing conversation during an incident is not a negotiation. Transputec covers the shape of that work as a named service rather than an exclusion buried in a monitoring contract: cyber incident response, run to NIST and ISO/IEC 27035 with analysts on a hotline. Ask us for the retainer shape now, which is the only sensible time to ask anyone.
Will you notify me if you are breached? This is the NCSC’s point above and it belongs in the contract, with a timeframe. A provider holds privileged access to your estate, which makes it exactly the kind of third party an attacker would prefer to compromise instead of you.
What an MSSP in London Costs, and What Sits Outside the Fee
Pricing in this market is quoted several different ways, which is the main reason quotes are hard to compare. You will see per user per month, per device, per ingested gigabyte of log data, per endpoint, or a flat platform fee with services layered on.
Per-gigabyte pricing deserves particular attention, because it is the model where your bill grows when you improve your security. Turn on verbose logging for a new system, or onboard a noisy application, and the cost moves without anyone deciding it should. Ask for a worked example at twice your current log volume before you sign.
The things that commonly sit outside the headline fee, and are worth confirming in writing:
Onboarding and tuning, which is usually where the first few months of value actually comes from.
Log retention beyond the included window, which compliance obligations may quietly dictate.
Incident response hours beyond triage.
Licences for the underlying platform, if you are expected to hold them rather than the provider.
Transputec publishes its own numbers rather than making you ask, in what round-the-clock monitoring really costs, and the detail of what sits inside the service in how a managed SOC works. Compare them against whatever else you are quoted. If a provider will not give you a shape of pricing before a discovery call, that is itself information.
Your Provider Is About to Become Regulated
One thing that should change how you write a contract signed in 2026 or 2027.
The Cyber Security and Resilience Bill will bring medium and large managed service providers into the UK’s NIS regulations for the first time, regulated by the Information Commission. The government’s factsheet on relevant managed service providers sets out the scope, and small and micro businesses are excluded. Once the regulations commence, a provider in scope has three months to register with the Information Commissioner.
The reporting duty matters more to you than the registration does. The incident reporting factsheet describes two stages: an early notice within 24 hours of becoming aware of an incident, and a fuller report within 72 hours, going to the regulator and the NCSC at the same time. The trigger is broader than an outage. It covers harmful breaches that have not yet disrupted services, with ransomware and pre-positioning given as examples.
Then the part worth reading twice. After the full notification, a provider has to identify the customers likely to have been adversely affected and notify them, with details of the incident and why they consider that customer affected. Your provider’s own breach stops being something you negotiate disclosure of and becomes something they owe you.
Two practical consequences. Ask where a provider is in preparing for this, because one that has mapped its obligations and can describe them is telling you something about how it is run, and a blank look is also an answer. And make sure the notification window in your contract is no longer than their regulatory one, or you will hear about your own incident from somebody else.
Since that question should be put to us as well, the answer is that Transputec will be in scope. With more than 120 specialists we are neither a small nor a micro business, so the registration duty and both stages of the reporting duty will apply to us once the regulations commence. We would rather you read that here than find it out halfway through a tender.
Transputec has set out what the Bill means if you are not regulated, which is the position most mid-market buyers are in: not directly in scope, but buying from somebody who will be.
How Transputec Works, Measured on the Same Criteria
In the interest of being judged against the same criteria as any other MSSP in London.
Transputec has been a London-headquartered managed service provider for 40 years, founded in 1986, with more than 120 specialists and over 1,000 projects delivered across cyber, cloud and AI. Those are the context numbers rather than the argument. The service is more specific.
Transputec runs six cyber security services behind one accountable UK SOC: a 24/7 managed SOC, ThreatSpike SOC, Microsoft Sentinel SOC, managed detection and response, penetration testing and vulnerability management. The sequence is assess, then protect, then monitor, and engagements start with an initial security assessment rather than a proposal, so the first thing you get is a maturity scorecard you can act on.
On the NCSC’s certification test, our certifications page lists ISO 9001 and ISO/IEC 27001, ISO 14001, and Cyber Essentials Plus against the implementation profile published in February 2025. Transputec is a G-Cloud 15 supplier and listed on the Government Commercial Agency framework. If a particular accreditation is written into your procurement rules, say so at the first conversation and you will get a straight yes or no that day rather than three weeks into a process.
On the questions this article tells you to ask, three of Transputec’s answers are already published rather than saved for a call. The service desk and Security Operations Centre are headquartered in London, in Wembley. Penetration testing runs with OSCP-certified UK senior testers, a free retest on critical findings, and scope to retest inside 30 days on most engagements. And the why partner page publishes the service desk’s current net promoter score next to the industry benchmark, which is an unusual number to put in public and a fair one to ask your current provider for.
Transputec’s security work is built for UK mid-market and public sector estates. For a London example at that scale, the Strand Palace Hotel work covers a 700-room London estate, moving it from reactive perimeter checks to proactive log monitoring and data loss prevention.
Where to Start
Choosing an MSSP in London is mostly an exercise in getting specific answers to a small number of questions, and the providers worth shortlisting are the ones who answer them without being chased.
Take the NCSC guide, pull out the certification, contract, access and patching requirements, and send them to three providers before you take a single demo. The replies will sort the list faster than any meeting. Then ask the bad-day questions: what you are authorised to do, what the response SLA actually measures, what happens when the incident exceeds the contract, and whether you will tell me if you are breached.
Judge the answers on specificity rather than confidence. Every provider on page one of that search sounds certain. Only some of them will put a number in a contract.
If the search that brought you here was for the best MSSP in London, the honest answer is that the phrase has no single winner. It has a provider that fits your estate, your obligations and your budget, and a longer list that does not. Transputec belongs on that list for UK mid-market and public sector estates, and the questions above are how you find out whether we belong on yours.
To put them to Transputec directly, talk to our team about the security work behind the headlines. We will take them in the order they appear above, and you should ask the other two providers on your list to do the same. And if you are earlier in the process and still deciding whether you need security monitoring or general IT support, choosing an MSP in London covers that question instead.
Frequently Asked Questions
What is the difference between an MSP and an MSSP?
An MSP runs your day-to-day IT: devices, service desk and infrastructure, judged on uptime and ticket resolution. An MSSP runs security operations: monitoring, detection and triage across your estate, judged on what it catches, how quickly, and who acts on it. Many firms provide both, but they are bought for different reasons and priced differently, so it is worth being clear which one you are actually buying.
How do I choose an MSSP in London?
Start with the NCSC’s free guide, Choosing a managed service provider, and turn its requirements into questions. Ask about certifications, how incidents are reported to you, who is accountable for damages, what access the provider needs, and patching timeframes. Then ask the bad-day questions: what the response SLA actually measures, what they are authorised to do without you, and what falls outside the contract during a real incident. Transputec answers that set on its cyber security services page and again in an initial security assessment rather than a proposal, and every provider on your shortlist should be willing to answer them in writing.
What certifications should an MSSP hold?
The NCSC recommends providers with recognised certifications such as Cyber Essentials Plus, and says ISO 27001 or SOC 2 demonstrate that an organisation takes information security seriously. Which ones matter depends on your own obligations: Cyber Essentials Plus carries weight in UK government supply chains, while ISO 27001 speaks to a managed information security system. Ask which certifications are current, and ask to see the certificate rather than the logo. Transputec holds ISO 9001, ISO/IEC 27001, ISO 14001 and Cyber Essentials Plus, and will confirm the current certificate for any of them on request.
How much does an MSSP cost in the UK?
It varies widely because providers price in different units: per user, per device, per endpoint, per ingested gigabyte of log data, or a platform fee plus services. Per-gigabyte models are the ones to scrutinise, since your bill rises when you improve logging. Ask for a worked example at twice your current log volume, and confirm in writing what sits outside the fee, typically onboarding and tuning, extended log retention, platform licences and incident response hours beyond triage.
Do MSSPs have to report their own security incidents?
They are about to. The Cyber Security and Resilience Bill brings medium and large managed service providers into the UK’s NIS regulations for the first time, with a 24 hour incident reporting deadline. Until then it is a contractual matter, so the NCSC advises specifying how incidents will be reported, including whether the provider will notify you if they experience one. Make sure your contractual notification window is no longer than their regulatory one.
This article was drafted with AI assistance and reviewed by the Transputec team. Featured image: AI-generated.
