East Sussex, but in all honesty, you can drive out of any town in Britian and end up in pretty little villages within 20 or so miles, even in built up places like Essex. (Its even possible to find villages inside London, where the city has grown around them - but they arn't that great looking anymore.)
Drive around Kent and hunt for Oast Houses.
Every county in Britain has an abundance of castles, and just about every village has ancient churches going back often as far as 1000+ years old. You can also find ancient earthworks, henges, forts, ect ... just by throwing a stone and seeing where it lands!