If i had a partner that couldn’t drive who wanted to maintain independence then i’d be moving to Bristol. It’s my favourite small city, you can walk from anywhere to anywhere and you’ve got great transport links and riding on your doorstep.
Has a lot going for it these days, regeneration of the docks has improved things no-end, excellent transport links, M4/M5 give access to pretty much anywhere quickly, as does Bristol Airport, the railway is currently being upgraded to high speed electric, there are loads of good pubs, music venues, and a new 12,000 capacity arena is being built right next to Temple Meads.
Dead easy to get out of the city by bike, it’s fifteen miles on the Sustrans path to Bath, or even further afield if you want.
I love Devon, but I wouldn’t go to the South coast with your caveats, get south of Exeter and the roads are very narrow, and slow; if you want to get to Kingsbridge or Dartmouth quickly, get behind a bus, because everyone else has to give way to it! 😉
If I drive down to South Hams, the last twenty miles from Exeter takes almost as long as driving from Chippenham to Exeter, and driving down to Weymouth is almost as bad; narrow roads, slow traffic, and zero passing places, I drove down to Charmouth earlier this year, got stuck behind a tractor and trailer doing 20mph for nearly eight miles before I found a stretch of road long and empty enough to pass.