Ben
(Ben)
4
Of what I’ve seen in the UK, all the county boundaries as well as district and parish boundaries are taken from Npemaps as has been said. Consequently it’s not always correct, and I know of quite a few errors which is frustrating. Another tecnquie has been to walk around spotting wheely bins and working out which streets belong to which county/district etc. I think this has mostly been done in London, maybe only London. Tracing these takes a long time though. Also, you may find this interesting, as it makes it clear what boundaries have and haven’t been done.