Anywhere north, including NE and NW: fenlands, i.e. marshes. Quite a few quarries as well. Extremely flat, very uniform, towns often have to be on top of small hills to escape the incessant flooding. Norfolk Coast AONB is beautiful if you take a train ride first, the beaches are very wide and many of them have few people if you avoid a few very busy spots.
East and SE: rolling hills towards Suffolk and the coast. Beautiful county, both Dedham Vale AONB and Suffolk Coast AONB.
South: first one of the hilliest nearby areas around Elmdon and Arkesden, then gently going down to the lush Lee River valley.
Southwest: larger and larger cities as you move towards London. From a train starting point, you can reach the Northen Chilterns, for some serious hills.
West: mostly flat farmland until you hit the River Great Ousse.