The verdict in three sentences
A website maintenance retainer for a B2B site costs between 300 and 1,500 GBP a month in London in 2026, and the price alone tells you nothing about what you are buying. What matters is the written SLA: response time, backup frequency, included hours and exit (reversibility) terms. If your 600 GBP retainer specifies none of these, you are paying for insurance with no cover.
What a maintenance retainer really covers in 2026
Website maintenance covers three families of work. Corrective maintenance fixes what breaks (a contact form that stops sending, a blank page after an update). Preventive maintenance applies security updates to the CMS, plugins and server, monitors uptime and tests backup restores. Evolutive maintenance adds small changes: a new page, an edited block, updated legal notices.
On a consultancy WordPress site running 15 to 25 plugins, expect 4 to 8 updates per month on average. A single unpatched vulnerable plugin is enough to get SEO spam or a malicious redirect injected. The retainer must state who applies these updates, how often, and who tests the site afterwards.
| Retainer level (London market 2026) | Monthly price | Security updates | Backups | Included hours | Response time |
|---|---|---|---|---|---|
| Basic, host or freelancer | 300 to 450 GBP | Monthly, automatic | Weekly | 0 to 1 h | 2 business days |
| Standard agency | 500 to 750 GBP | Twice monthly, tested | Daily, 30 days | 2 to 3 h | 1 business day |
| Enhanced | 800 to 1,100 GBP | Weekly + critical patches within 24 h | Daily off-site, 90 days | 4 to 5 h | 8 business hours |
| Premium with on-call | 1,200 to 1,500 GBP | Continuous + web application firewall | Daily + before every update | 6 to 8 h | 4 h, including Saturdays |
| Ad hoc, no contract | 90 to 140 GBP/h | None | None | 0 | Subject to availability |
These amounts are 2026 orders of magnitude observed in the London market, not an official rate card. A 600 GBP retainer is consistent with the Standard level, provided it really includes daily backups and 2 to 3 hours of changes.
The SLA clauses that make the difference
The SLA (service level agreement) turns a vague promise into a measurable commitment. When reviewing your contract, look for the seven clauses below. If one is missing, ask for an amendment before the next renewal.
| Clause | Wording to require | Warning sign |
|---|---|---|
| Response time | "Acknowledged within 4 business hours for a blocking incident" | "As soon as possible" |
| Resolution time | Blocking 8 h, major 48 h, minor 5 days | Only a response time, no resolution time |
| Uptime | 99.5 % monthly minimum, measured by an external probe | No measurement, or host-only measurement |
| Backups | Daily, stored off-server, quarterly restore test | "Regular backups" with no frequency |
| Included hours | 3 h/month, rollover up to 3 months | Hours lost every month, no time log |
| Service credits | 10 % of the monthly fee per day of delay beyond the target | No credits |
| Exit terms | Handover of access, code and database within 10 business days, free of charge | Admin access kept by the supplier |
Exit terms are the most frequently forgotten clause. Check that the domain name is registered to your company, that you hold an administrator account and that the hosting can be transferred. Without this, switching supplier can cost 2,000 to 4,000 GBP in rebuild work.
Also request a monthly report: updates applied, backup results, uptime, hours consumed. A serious supplier produces it in minutes from its monitoring tools.
Mini case study
Laura, office manager of an 18-person consultancy in London, has paid 600 GBP a month for three years, or 7,200 GBP a year. Rereading the contract, she finds weekly backups kept for 7 days, no written response time and out-of-scope hours billed at 110 GBP. Over the past year she paid 8 extra hours of changes, or 880 GBP. Real cost: 8,080 GBP.
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She consults two suppliers. Chosen offer: 650 GBP a month with daily backups kept 90 days, 3 included hours with rollover, 8-business-hour response and an exit clause, or 7,800 GBP a year. The 8 hours of changes now fit inside the retainer. She saves 280 GBP a year and, above all, gets written guarantees. This case is an illustrative example.
FAQ
What does a website maintenance retainer cost in London in 2026?
The usual range is 300 to 1,500 GBP a month. For a 10 to 30 page B2B site on WordPress, the Standard level at 500 to 750 GBP covers most consultancies and SMEs.
Is a site without maintenance really at risk?
Yes, a WordPress site left unpatched for 6 months often accumulates several known plugin vulnerabilities. Cleaning a hacked site usually costs 500 to 1,500 GBP, before counting the ranking loss if Google flags it as dangerous.
What does TMA or application maintenance mean in a contract?
Third-party application maintenance groups fixes and small changes handed to an external supplier. In a website retainer it means 1 to 8 included hours a month, to be checked in the contract.
Can I terminate a maintenance contract mid-year?
It depends on the commitment, often 12 months auto-renewing with 1 to 3 months' notice. Negotiate a 30-day notice exit after the first year.
Does a simple brochure site need an SLA?
If the site generates meeting or quote requests, yes. A contact form down for 5 days can lose several prospects, and a written 24 to 48 h resolution time limits that risk.
Let's scope your project. Send us your current contract: we review it and propose a maintenance retainer with a written SLA, daily backups and exit terms, with an indicative budget and a takeover date. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
