Office for National Statistics Unique Property Reference Number (UPRN) Directory
The ONSUD allocates addresses directly to a range of administrative, health, and other geographies using the grid reference of the UPRN (Unique Property Reference Number) and point-in-polygon methodology.
Office for National Statistics
The Office for National Statistics (ONS) collects, analyses and disseminates statistics about the UK's economy, society and population
https://www.ons.gov.uk/