I recently spent a week biking in SW England (Devon) & SE England (East Sussex & Kent), with a train connecting the 2 areas. I had toured in areas in-between many years ago. Most of the cycling in England on this trip sucked for the reasons you described, as well as the trails which were of inconsistent quality which ranged from good to appalling. I didn't feel that the Sustrans descriptions were always accurate. I spent considerably more time on this trip cycling in France (3 regions: west-central France, northern Brittany, & Picardie). The biking in all of these regions of France was far better than the biking in southern England. The last time I had biked in the UK I was in western Scotland and a bit of Yorkshire. Both were nice and much more enjoyable than any biking I experienced in southern England this year. While I've never had an issue adjusting to biking on the left, the road quality in southern England was much worse than in France, drivers weren't as polite to cyclists as in France, and traffic was heavier than in France. The narrow roads with no shoulder combined with the hedgerows made for some occasionally scary riding. I have to wonder how many head-on collisions happen on those curvy narrow roads with hedgerows. In one area I had to resort to riding on a road with fast-moving traffic because the trail was unridable due to mud. (I had fairly wide tires & fenders, which worked well on the GAP & C&O Canal.)

There were certain places I wanted to see in both SW England & SE England, and I did very much enjoy the towns of Bath and Canterbury, as well as several gardens I wanted to visit--English gardens are fantastic. As for food, yeah England was more expensive than France, though I love South Asian food so I took advantage of the multitude of Indian/Pakistani/Bangladeshi restaurants for dinner. I wasn't camping and hotels and B&Bs are generally a better value in France, too.