The verdict in three sentences
A badly planned migration can wipe out 10 to 40 % of organic traffic for months, and the same share of inbound enquiries. Your best insurance is a pre-migration SEO audit (GBP 1,500 to 6,000) followed by a complete 301 redirect map and 3 months of Search Console monitoring. Put the 8 questions below to every agency you shortlist: their answers show whether they understand migrations or only design.
Questions to ask, with good and bad answers
| Question | Good answer | Bad answer |
|---|---|---|
| 1. Do you run an SEO audit before the rebuild? | « Yes: full URL export, pages with traffic and backlinks, GBP 1,500 to 6,000 » | « We'll look at SEO after launch » |
| 2. How will you handle redirects? | « URL-by-URL 301 map, signed off by you, tested before go-live » | « We'll point everything to the homepage » |
| 3. How many URLs need redirecting? | « Our crawl shows 1,800 URLs, 420 with traffic » | « None, URLs stay the same » without checking |
| 4. Will staging be blocked from Google? | « Yes, password-protected, noindex removed at launch » | « It's live on a public subdomain » |
| 5. What happens to existing content? | « High-performing pages are kept or expanded » | « We'll simplify to 6 pages » |
| 6. What monitoring happens after launch? | « 3 months in Search Console, weekly report for the first 4 weeks » | « The project ends at handover » |
| 7. What if traffic drops more than 20 %? | « Diagnosis within 48 hours, fixes included » | « That's normal, just wait » |
| 8. Who owns the accounts? | « You do: Search Console and Analytics stay in your name » | « We manage everything on our accounts » |
If an agency gets more than two of these wrong, drop it, however strong the design portfolio.
Budget and timeline for a safe migration
For a London SME with 300 to 3,000 URLs, here are the SEO line items to expect in the quote, as 2026 estimates excluding VAT.
| Stage | Duration | Cost | Deliverable |
|---|---|---|---|
| Pre-migration SEO audit | 1 to 2 weeks | GBP 1,500 to 6,000 | URL inventory, top pages, backlink profile |
| 301 redirect map | 3 to 10 days | GBP 800 to 3,000 | old URL to new URL spreadsheet |
| SEO QA on staging | 3 to 5 days | GBP 500 to 1,500 | tags, internal links, speed, structured data |
| Go-live and testing | 1 day | included | 100 % of redirects tested |
| Search Console monitoring | 3 months | GBP 600 to 2,000 | reports and fixes |
| SEO workstream total | 6 to 8 weeks + 3 months | GBP 3,400 to 12,500 | migration without lasting loss |
This typically represents 15 to 25 % of the total rebuild budget. Also check that cookie consent and analytics are configured in line with UK GDPR and PECR on the new site, since a broken consent banner can distort your post-launch data.
The costliest mistakes
Mass redirects to the homepage are the first: Google treats them as soft 404s. An indexed staging site is the second, creating duplicate content. Deleting pages that looked minor but carried traffic is the third. Each one alone can cause a 10 to 20 % drop.
Mini case study
Illustrative example: Tom, digital lead at a 40-person commercial fit-out company in Southwark. The site generates 60 enquiries a month, 60 % from Google, so 36. A rebuild without SEO planning would cost an estimated 30 % of organic enquiries for 4 months.
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Loss avoided: 36 x 30 % x 4 = about 43 enquiries. At a 20 % win rate and an average project of GBP 45,000, that is roughly 8 projects and GBP 360,000 in revenue. The SEO workstream costs GBP 7,000, a return of more than 50 times.
FAQ
How much traffic can a bad migration lose?
Typically 10 to 40 % of organic traffic for 2 to 6 months. Without proper redirects, part of it can be lost for good.
What does a pre-migration SEO audit cost in London?
GBP 1,500 to 6,000 depending on URL count. The full SEO workstream runs GBP 3,400 to 12,500.
How long should we monitor after launch?
At least 3 months in Search Console. The first 4 weeks are critical, which is why weekly reporting helps.
Should we keep the same URLs?
Ideally yes, but only an audit confirms it. On 300 to 3,000 URLs, some almost always change.
Can a staging site hurt rankings?
Yes, if Google indexes it you end up with two versions of the site. Password protection fixes it in minutes.
Get found by the buyers already searching for you, before and after the rebuild. Start with a visibility audit at 100,000 FCFA (about EUR 152, credited against the setup if you start within 30 days), then protect what follows with a Traffic Engine plan and a weekly report on rankings and enquiries. Traffic Engine. 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.
