We have a smattering when the enthusiastic have started them but it's patchy.
Naming conventions: use your best judgement but go with what makes it easiest for people to find - if there's more than one name go with the English for now and you can save the, for example, Welsh one for a Welsh-language community.
edit: as discussed in the comments, you may be better off with a more regional community first - those like London, Manchester and Liverpool already function like that as they cover the greater city area. So instead of Chelmsford and Southend, start one Essex; instead of Lancaster, start one for Lancashire. At least initially until things really get going here. That list is over here.
The list:
- Aberdeen
- Armagh
- Bangor, Northern Ireland
- Bangor, Wales
- Bath
- Belfast
- Birmingham
- Bradford
- Brighton and Hove
- Bristol
- Cambridge
- Canterbury
- Cardiff
- Carlisle
- Chelmsford
- Chester
- Chichester
- Colchester
- Coventry
- Derby
- Derry
- Doncaster
- Dundee
- Durham
- Edinburgh
- Ely
- Exeter
- Glasgow
- Gloucester
- Hereford
- Inverness
- Kingston upon Hull
- Lancaster
- Leeds
- Leicester
- Lichfield
- Lincoln
- Lisburn
- Liverpool
- London (technically City of London is one too but let's not split hairs at this point)
- Manchester
- Milton Keynes
- Newcastle upon Tyne
- Newport
- Newry
- Norwich
- Nottingham
- Oxford
- Perth
- Peterborough
- Plymouth
- Portsmouth
- Preston
- Ripon
- Salford
- Salisbury
- Sheffield
- Southampton
- Southend on Sea
- St Albans
- St Asaph
- St Davids
- Stirling
- Stoke-on-Trent
- Sunderland
- Swansea
- Truro
- Wakefield
- Wells
- ~~Westminster~~ - stick to London for now
- Winchester
- Wolverhampton
- Worcester
- Wrexham
- York
edit: adding in links to existing ones