Thought of a few more
Launceston (cornwall. Lovely town with castle and big Christian bookshop with a basement for second hand books and lovely fish and chips)
Wetherby (n. Yorks)
Framingham Earl ( Norfolk broads. Beautiful little village not too far from Norwich which is a town with a nice vibe)
Chesterfield! (Derbyshire/ s York border) quirky market town with some great shops, market , a decent sized Waterstones and a bakery that does oatcakes (similar to Staffs oatcakes, big, floppy) and lovely pork and stuffing rolls. Plus the church with a corkscrew spire, due to lead melting, but there are some colourful local legends about its shape),
Seaton and Beer area in East devon. Actually not so sure Beer underrated, it seems quite popular but Seaton (and neighbouring Colyton) sure are. You can see little egrets and herons on the river and there are tram rides.
Twerton (Bath) just outside Bath, nice little town full of pubs and traditional style bakery, lovely 18th and early 19th century buildings. Also Weston village around Bath Royal United Hospital. A tiny village but with a fantastic Chinese chip shop and a lovely cafe which does a smashing avocado on toast. Victoria park is there with huge play area for children
Frome (also n Somerset ) some lovely historical buildings. very pretty place