Microsoft 365 migration for small businesses in London: what to plan for

The triggers we see are predictable. A landlord changes and the building's old phone-and-email service stops being economic. A funding round comes in and the investors expect proper security controls. A cyber insurance renewal asks questions the current setup can't answer truthfully. A founder leaves and takes the keys to the GoDaddy account with them. An accountancy or legal client demands secure file sharing the existing tools can't do.

Underneath those triggers, the common driver is that the business has outgrown a setup that was put together by whoever was around when the company was three people. Microsoft 365 is rarely the most exciting answer, but it's the one that scales, the one auditors and clients recognise, and the one most other tools in the stack already integrate with.

For a typical 10-to-80-person London SME, a sensible migration runs across three to six weeks of calendar time, with the heavy lifting concentrated in two evenings. Week one is discovery, picking the right licence plan, designing the tenant, and an honest look at the existing file mess. Weeks two and three are setup: tenant configured, accounts created, security baseline applied, Teams and SharePoint structure agreed, and a pilot group moved.

The cutover weekend is when MX records flip and the rest of the mailboxes land. Done with a proper migration tool, staff arrive on Monday with their email already in place and a short briefing on the new Teams and OneDrive. Weeks four to six handle the inevitable tail: the printer that doesn't authenticate, the line-of-business app that's still pointing at the old SMTP relay, and the one director who insists on Outlook 2013 on a personal laptop.

Email migrations are well-understood and the tooling is good. The bit that derails London SME migrations is files. A typical 30-person business has a tangled file server, a Dropbox account someone set up in 2019, a SharePoint site from a previous attempt, and several gigabytes of important documents in personal OneDrives that aren't backed up by anyone.

Good migrations don't try to fix all of that in one weekend. They move the active 20 percent that people actually open, leave the rest in a read-only archive for six months, and use that window to agree a sensible SharePoint structure with each team. Trying to lift-and-shift the lot at once is how you end up with a SharePoint tenant nobody trusts and a quiet retreat back to Dropbox.

London SMEs in regulated sectors, financial services, legal, accountancy, healthcare adjacent, have a slightly heavier checklist than the general market. FCA-supervised firms care about email retention and supervision. Law firms care about SRA (Solicitors Regulation Authority) expectations on client data. Accountancy practices care about ICO-aligned handling of personal data and increasingly about Cyber Essentials Plus for client contracts.

Microsoft 365 can meet all of those expectations, but only with the right plan and a few extra configuration steps. Business Premium is the right floor for most of these firms because it includes Defender for Business, Intune, Azure AD Premium P1 (Conditional Access and MFA), and the Purview tools needed for retention and DLP. Stepping up to E3 or E5 is only worth it for genuinely larger or more regulated firms, and a good partner will tell you that rather than upsell you by default.

Microsoft 365 Business Premium is around £18.10 per user per month and is the right starting point for most London SMEs. Business Standard at around £10.30 is cheaper but skips the security tooling that's usually the reason for moving in the first place. For a 30-person firm, you're looking at roughly £6,500 a year in licences and somewhere between £4,000 and £15,000 in project costs to migrate properly, depending on how messy the starting point is and whether you're moving from on-prem Exchange or just consolidating cloud tools.

The cheaper end of that range usually means email-only, no file rationalisation, no security hardening. The upper end usually means file structure designed with each team, security baseline applied, devices brought into Intune and a short period of hand-holding post go-live. The total cost of a botched cheap migration almost always exceeds the cost of a proper one within 12 months, so it's worth getting honest quotes from two or three partners rather than picking the lowest number.

Most of the partners pitching Microsoft 365 migration in London are competent enough to move mailboxes. The thing that separates them is what they do around the move. Will they design the SharePoint and Teams structure with each function, or just create one site and walk away. Will they configure Conditional Access and MFA from day one, or leave you exposed for 90 days. Will they enrol devices into Intune at the same time, or quote that as a follow-on phase. Will they hand over a short runbook and a named contact, or disappear once the invoice is paid.

If a partner can't answer those questions concretely, with examples of recent London clients of similar size, they're not the partner you want for this. Tell us your team size, current setup and what's prompting the move. We'll introduce you to a London partner who's done this exact pattern many times and will be honest about what's involved.