OS Boundary-Line - GPX file download
Converted from the May 2021 issue, released May 2021 by Ordnance Survey
Historic Counties of England, Scotland and Wales
Ceremonial Counties of England, Scotland and Wales
Administrative Counties of England
Districts, Boroughs and Unitary Authorities of England, Scotland and Wales
English Civil Parishes and Welsh Communities
Unparished areas
High Water Mark (useful for some coastlines)