Ordnance Survey OpenData
Ordnance Survey OpenData is the free tier from Great Britain's national mapping agency, offering complete, consistent, and seamless coverage of England, Scotland, and Wales. It includes building outlines, road classifications, greenspaces, administrative boundaries, unique property and road reference numbers, postcodes, and key topographic features, all maintained to the standard you would expect from the official mapmaker rather than a crowdsourced effort.
A handful of products do most of the work. Boundary-Line holds every administrative boundary in Great Britain, from parliamentary constituencies to parish edges. Code-Point Open lists all current postcode units with coordinates. OS Open Names is a gazetteer of place names, road numbers, and postcodes, and OS Open Greenspace maps parks, sports facilities, play areas, and allotments. MiniScale gives you a lightweight national backdrop map. Everything is served through the OS Data Hub, with downloads and APIs in formats including GeoPackage, GML, Shapefile, and CSV.
For RAG, this is the authoritative base layer for any UK location-aware system: resolving postcodes to places, answering questions about administrative areas, or grounding a service in real British geography. The usual pattern is to flatten the features you need, such as a place name with its type, postcode, and boundary, into short text records you can embed and retrieve, since geospatial formats are not searchable prose on their own. OS Open Names in particular converts cleanly into a place lookup.
Two things to plan for. Reuse under the Open Government Licence v3.0 permits commercial use but requires attribution: "Contains Ordnance Survey data © Crown copyright and database right [year]", and Code-Point Open additionally requires Royal Mail and National Statistics attribution statements, so keep those notices with anything you publish. Coverage is Great Britain, so Northern Ireland is not included, and OpenData is deliberately a subset: Ordnance Survey's most detailed products sit behind paid premium tiers. For crowdsourced richness such as points of interest and opening hours, pair it with OpenStreetMap, which fills gaps OpenData leaves open.
Related sources
Companies House
The UK's official register of companies. Search every registered company, its directors, filing history, and accounts, or pull the data in bulk. A reliable source for UK corporate facts in a RAG system.
data.europa.eu
The European Data Portal, a single point of access to open data from 36 European countries and the EU institutions. Over 1.6 million datasets span every policy area, giving RAG systems broad, multilingual coverage of official European data.
data.gov
The US federal government's open data portal, gathering more than 300,000 datasets from federal agencies. Coverage spans agriculture, climate, education, energy, finance, health, and public safety, making it a broad source of official US data for RAG systems.
data.gov.uk
The UK Government's central catalogue of open public sector data, run by the Government Digital Service. More than 47,000 datasets cover health, housing, transport, demographics, and the environment, giving RAG systems a trusted base of UK facts, figures, and official records.