This document provides information about how the census and administrative area location fields were derived, including differences between area definitions for England and Wales vs Scotland, and the data sources used.

This resource can be downloaded or viewed using the link: census_admin_areas.pdf

If you have wget available (typically on linux systems), then you can also obtain a copy using the command

 wget  -nd  biobank.ctsu.ox.ac.uk/ukb/ukb/docs/census_admin_areas.pdf