Best - Depends where you like, personally I'd like to live on the coast in Devon somewhere or a cute town like Warwick. I'd hate to live in a place that was completely inaccessable really, such as a small village. Then again, some people might love to live by the city, for the variety.
Worst - Major cities, I live not far from Birmingham and going into Birmingham and the city itself, it's horrible. It's too dirty, too many people and aside from the diverse shopping it's not that great.