The Local Authorities for England Register has been developed with the UK Department for Communities and Local Government (DCLG), and contains identifiers for 350+ local authorities. It also includes the 'local authority type' (e.g. Unitary Authority, London Borough) for each.
It uses the second portion of [ISO_3166-2](https://en.wikipedia.org/wiki/ISO_3166-2:GB) codes where these are available, and creates new codes where they are not. For more information on GOV.UK Registers, visit https://registers.cloudapps.digital/