Measurement
Using ONS and Companies House data for UK local SEO market research
Local SEO market research gets sharper when you size UK local markets with named ONS datasets and Companies House filings rather than guessing.
What to take away
- Four ONS products carry the sizing workUK Business Counts, Business Demography, the Business Register and Employment Survey, and the Business Population Estimates.
- Count competitors from the Companies House register by SIC code and postcode district, then divide by ONS business counts.
- Add demand from Google Keyword Planner, Google Trends, Ahrefs or Semrush and Google Business Profile insights.
- Multiply a realistic client count by a labelled retainer input and publish a low and high case.
Run the six-step sizing model
The arithmetic is simple, and each step should hold up on its own.
- Pick the geographya local authority district for a town pitch, a region such as the North West for multi-site operators.
- Pull the ONS business count and keep the size bands that fit your minimum viable client.
- Filter Companies House by SIC code and postcode district, keeping active entities only.
- Divide active competitors by the ONS business count for a density ratio.
- Add a demand column from a keyword tool and Google Trends.
- Multiply the realistic client count by a retainer, then publish a low and high case.
Six steps to size a local market
- Define the geography
- Pull business population estimates
- Pull active Companies House entities
- Calculate density ratio
- Add demand evidence
- Apply conversion and fee assumptions
A single number implies a precision that official data cannot support. Our walkthrough of local SEO market size in England runs the same method in a copyable spreadsheet.
ONS datasets to name in a market model
Name the product, not the theme. Four do most of the work.
- UK Business Counts, from the Inter-Departmental Business Register (IDBR), counts VAT and PAYE registered businesses by local authority, industry and size band.
- Business Demography covers births and deaths, which is churn.
- The Business Register and Employment Survey (BRES) gives employment by industry and place.
- The Business Population Estimates give private sector counts, registered and unregistered, with regional breakdowns.
The business statistics published by the Office for National Statistics hub lists current releases and reference periods, so cite the release, not the theme. Local authority boundaries have changed in parts of England, so check the geography column.
Count competitors with Companies House filters
The Companies House register holds every incorporated UK entity, with SIC codes, registered offices and filing history. Filter in this order:
- SIC codeyour client's category plus adjacent codes for the same service.
- Postcode district, such as M4 or B1, which matches how local results behave.
- Company statusactive only.
- Accountsexclude dormant filings.
- Group structureremove holding companies that duplicate a trading entity.
Registered offices are not trading addresses, so formation agents cluster thousands of companies into city centre postcodes. Our local SEO competitor research checks test these filters against real district data.
Example: density in two named postcode districts
Density in two postcode districts
| District | ONS businesses | Active competitors | Density ratio |
|---|---|---|---|
| M4, Manchester | 4,000 | 240 | 0.060 |
| B1, Birmingham | 1,200 | 90 | 0.075 |
Treat these counts as illustrative until you pull the live releases. B1 is smaller in absolute terms but more crowded against its own business base, so the same effort buys less.
Compare density ratios, not headcounts. A ratio of 0.075 means seven and a half competitors per hundred businesses.
Turn density and demand into a retainer estimate
Demand tools: Google Keyword Planner, Google Trends, Ahrefs or Semrush, and Google Business Profile insights for the client's own queries.
Divide monthly category searches by the district business count. That fraction, not the whole business population, is what you sell against.
Multiply the realistic client count by a monthly retainer input. An illustrative England band of GBP 600 to GBP 1,800 per month is a figure to test, not a published rate. Compare local SEO pricing in London, Manchester and Cardiff before quoting.
State each limit once
- ONS counts lag, often by more than a year.
- The register covers registered entities, not trading ones.
- Registered offices cluster in city centres.
- SIC codes are self-reported and imperfect.
A ratio from a lagged release still ranks districts against each other reliably, which is the comparison a client pays for.
Structure the findings for a client
Lead with the decision and keep the method in a one-page appendix. Five parts work: the recommendation, the density and demand table, the revenue range, the assumptions and the refresh date.
Close with the competitive picture. Name the crowded districts, the underserved ones, and where the next pound of spend buys the most visibility.
Any published claim must not mislead, so keep the range and the source date beside the number, as the ASA misleading advertising rules require.
Common questions
Which ONS datasets should I use for UK local market sizing?
UK Business Counts for the business denominator, Business Demography for churn, BRES for employment, and the Business Population Estimates for headline counts.
How do I count competitors with SIC codes and postcodes?
Filter the Companies House register by SIC code and postcode district, keep active status, drop dormant accounts and remove holding companies.
How do I calculate competitor density?
Divide active competitors in the district by the ONS business count for the same geography, then report the ratio rather than the raw count.
