SEO Migration Review: Agency Briefing for a Large UK Website
A UK-wide training and consultancy organisation was preparing to commission a full website rebuild. On the surface, it looked like a fairly contained piece of migration preparation.
Once I crawled the existing site, it turned out to be bigger and more complicated than the visible website suggested.
I was brought in through the organisation’s project manager to work out what needed protecting, flag the main SEO migration risks, and turn all of it into a brief the appointed agency could use.
Project Summary
Client: UK-wide training and consultancy organisation
Project: SEO migration review and agency briefing
Scope: Technical crawl, analytics review, backlink evidence, page performance, AI visibility and migration controls
Delivery: Completed within a two-day project allowance
Core focus: Protecting existing search value before a major website rebuild
4,000+ URLs
Reviewed across the site
Around 25% organic search
Of total website traffic
2-day delivery
From kick off to final briefing
The Challenge
The organisation was planning a substantial rebuild but had no technical SEO expertise in-house.
The project manager understood the risk: a rebuilt website can improve the design and still lose search visibility if URLs, content, internal links and tracking change without a plan.
There was also a gap in the evidence. Search Console had only just been set up, so there was no useful history of search queries, impressions, rankings or indexation. GA4 data existed, but I could only access it indirectly, through exports the project manager pulled for me.
Then the crawl changed the scale of the job. It turned up more than 4,000 internal URLs, including a substantial legacy footprint of articles, team profiles, case studies, services, jobs, downloads and older paths.
A robust page-by-page decision on every one of those was not realistic in the time available. It would also have been premature before the agency had proposed the new site structure.
So we agreed a focused scope: build the evidence, flag what mattered most, and set clear requirements for the migration itself.
The Approach
Establishing the real scale of the website
I ran a licensed Screaming Frog crawl to build a technical baseline of the site: its URL footprint, status codes, redirects, indexability, canonical tags, XML sitemap, internal links, metadata, headings and image issues.
Much of the website’s value sat well beyond the main navigation. Plan a rebuild around the visible menu alone, and you could miss a lot of existing content and search value.
Backlink checks confirmed real external authority worth protecting too, including links pointing at older versions of the domain and individual pages.
Understanding what needed protecting
GA4 showed that Organic Search was a significant source of traffic, accounting for around a quarter of all sessions.
That value was spread across the site rather than sitting only on the homepage or main service pages. Articles, team profiles, case studies and several functional areas were all contributing.
Without historic Search Console data, I had to treat the evidence carefully. Low recorded traffic became a reason to look closer, not a reason to delete.
Turning the evidence into migration requirements
The core recommendation was simple: treat the rebuild as a controlled SEO migration, not just a redesign or a CMS swap.
I built a preserve-before-improve framework. Keep important URLs and sections in place where practical. Where URLs do change, redirect them cleanly to the closest replacement. Use the rebuild as a chance to fix existing technical issues rather than carry them into the new site.
The final agency pack set out clear requirements covering:
URL preservation and redirect mapping
HTTPS and preferred-domain handling
Canonical tags and XML sitemaps
Indexation and robots controls
Internal links
Analytics and form tracking
Page performance
Pre-launch and post-launch validation
AI-assisted analysis helped me work through the volume of crawl and analytics data, but nothing went into the final documents unchecked. Every material conclusion was tested against the underlying evidence first.
Outputs
Executive Summary
A concise overview of the main findings, risks and priorities for the project manager and leadership team.
Agency Briefing
Clear SEO migration requirements covering URLs, redirects, indexation, tracking and launch checks.
Evidence Pack
The supporting crawl, analytics and technical evidence behind the recommendations.
The Result
The project produced two levels of output.
The first was a concise executive summary, which the project manager used to brief the organisation’s non-technical leadership. It explained the scale of the site, the main risks and what the rebuild needed to protect.
The second was a detailed agency brief and evidence pack, including a section-level migration framework and practical checklists for before launch, launch day and the weeks after.
That gave the project manager a clear basis for briefing prospective agencies and checking whether their proposed process covered the risks. One prospective agency welcomed the fact that the crawl and evidence base were already in place. It clarified what formed part of their standard process and what would have to wait for the new site structure.
The rebuild had not happened by the time my engagement ended, so this is not a case study about a ranking increase. The value came earlier: the organisation now has a much clearer picture of what it has, what is at risk, and what it needs from the agency doing the rebuild.
“Jonny delivered a thorough agency brief, including core principles, key SEO risks detailed by category, requirements for sections, redirects, page performance and AI visibility, and a timeline for checks, together with a full evidence base of documentation. The project was delivered confidently and well, to time and to budget. It has delivered a useful resource at this stage in the process, and will be a support to the team and to the project as a whole.”
Laura T, Project Manager
Planning a website migration?
A rebuild can improve clarity, usability and performance. It can also cost you years of search visibility if your URLs, content, links and tracking change without a plan.
I help organisations work out what needs protecting, then turn the technical evidence into practical requirements the agency can be assessed against before anything irreversible happens.
Get in touch to talk through what your migration needs.