Norfolk is great for 3-4 days of easy touring. Best airport is Stansted. You can get the train to any station up to Norwich.
Lots of US links and history, pretty villages, big country houses, castles, pubs, fantastic N coastline, endless network of quiet country lanes although secondary B roads can be busy.
The terrain is very gently rolling with a few small hills along the coast, and dead flat in the eastern part ( the Fens) towards Ely and Cambridge.
There is a new national park of lowland lakes and rivers ( The Broads) which is accessable by bike.