Too hard to choose really
Town .... Lichfield (or is it a city?), Ludlow, Knaresborough, shout out for Steyning in Sussex, Alnwick, Lyme Regis, Beaumaris, tons in Wales tbh...Solva is more a village I think
City.... Newcastle, Durham, Glasgow, Edinburgh, Birmingham, London, York, St David's, Dundee, all got loads going for them and a soft spot for Brighton and Hove.
Britain is a wonderful place really despite the gloom. We have some beautiful towns and cities. It's also how you feel when you're there and what memories they bring back. All the above have happy memories for me.