How to Find UK Companies by Postcode for Local B2B Outreach

If you're a local services business, a regional accountant, a city-specific recruiter, a Manchester web agency, your prospect list lives or dies on postcode-level filtering. "All UK companies in our SIC code" is too broad. "Companies in the towns and postcode districts we cover" is what you actually want. Here's how to do that on Companies House data.

Why postcode filtering is harder than it looks

Companies House publishes the registered office address for every UK limited company, including the postcode. So in theory, filtering by postcode is trivial. In practice there are three gotchas:

1. Registered office ≠ trading address

Many small companies use their accountant's address or a virtual office as the registered office. So "companies registered at PO Box 1234, Manchester" includes a lot of businesses that don't actually trade in Manchester. For high-precision local prospecting, you usually want to *cross-check* with the company's website (which often has a real address) or with directors' service addresses.

2. Postcodes have multiple useful levels

UK postcodes are hierarchical:

• Area (one or two letters), such as SE, M or BT: covers a region
• District (the area plus one or two digits), such as SE1, M1 or BT1: covers a town or part of a city
• Sector (the district, a space and one digit), such as SE1 7: covers a few streets
• Full postcode, such as SE1 7TJ: covers a handful of addresses, sometimes one building

For local prospecting, postcode area (SE, M, etc.) is usually too broad and full postcode is usually too narrow. The sweet spot is postcode district, "SE1, SE2, SE3, SE4..." for a south-east London accountant.

3. SIC + postcode combined is the magic filter

A list of "all companies in SE1" is unwieldy. A list of "construction companies in SE1, SE2, SE3" is a workable outreach queue. See our SIC code guide for the right SIC clusters by sector.

Doing it on Companies House data

Companies House's own advanced search does more than most people expect. Its registered office address box takes a full or partial address, such as a town or a postcode district like SE1, and you can combine it with SIC codes, company status and an incorporation date. It downloads the first 5,000 results as a CSV file. What it cannot give you is anything the register does not hold: there is no filter for employee numbers, because the register has no headcount field, and there are no websites or emails. For more than 5,000 rows, or many districts at once, you need either the bulk data files or a tool that has already done the filtering work.

If you want to DIY:

1. Download the monthly Companies House bulk file, one large CSV with about five million companies in it.
2. Load it into a database such as Postgres or BigQuery.
3. Keep the active companies whose registered-office postcode district is one of yours (SE1, SE2 and so on) and whose SIC codes include the ones you sell to, such as 41201 and 41202.
4. Find a website and an email for each one by hand.

If you want a tool, Leadistry does this from a sentence. Say which trades you sell to and which towns or postcodes you cover. The setup chat picks the SIC codes and the area, and shows you real sample companies before anything is charged.

Postcode-area cheat sheet

UK B2B services often map to specific postcode areas. A few common ones:

• E, EC, N, NW, SE, SW, W, WC, central and inner London (E is east London, and so on). Outer London boroughs sit in areas that reach beyond London too, such as BR, CR, HA, KT and TW.
• B, Birmingham
• M, Manchester
• L, Liverpool
• LS, Leeds
• NE, Newcastle upon Tyne
• S, Sheffield
• G, Glasgow
• EH, Edinburgh
• CF, Cardiff
• BT, Belfast (Northern Ireland)

For a sales rep covering "the North", the typical cluster is M, L, LS, S (Sheffield), HU (Hull), HD (Huddersfield), BB (Blackburn), PR (Preston). For "the South West", BS (Bristol), BA (Bath), TA (Taunton), EX (Exeter), PL (Plymouth), TQ (Torquay).

Common mistakes

• Filtering on registered office only, picks up a lot of accountant addresses. Cross-reference with website addresses where possible.
• Going too narrow: a postcode sector such as "SE1 7" covers a few streets, so the list is small, and one accountant's or formation agent's address can make up much of it. Postcode-district level is usually the right grain.
• Ignoring postcode plus SIC: a postcode on its own can still mean tens of thousands of companies in a busy area. Always combine it with an industry filter.

If local prospecting is your main use case, Leadistry's postcode + SIC + age filters cover the common patterns out of the box. The free trial is 25 leads, once, with no card.