I go to Essex 2-3 times a year, having family in the county. A large portion of Essex is on the border with Greater London.
Waltham Abbey is closer to London. For picturesque Essex market town Saffron Walden might work. It was voted as one of the best places to live recently. It has good links from London Liverpool Street Station with just a short taxi ride from Audley End station. (Audley End house is also wonderful with fabulous gardens). Cambridge would be a very short stop next on the main line, which would be a great place to visit. Ely is the nexct stop on the line and has a wonderful Cathedral.
Transportation links from London also go to Colchester where you have Dedham & the Dedham Vale (Constable Country - famous painter of scenic landscapes). You would need a taxi from either Colchester or Manningtree rail stations to reach these parts. Colchester, (IMO) is not the town it used to be. It has a Norman Keep on an Old Roman site, but the market town is a little worn and not much to see (I can say this as I was born there). The coastal towns mentioned, are not very glamourous. Ok, for a day trip for locals, but not much of interest, and the North Sea is cold and brown. Chelmsford, Braintree, Witham are all serviced by trains out of London, but they are not what you are looking for. Maldon is not easy to get to. Coggershall is a nice village (train to Marks Tey towards Colchester) with Taxi to the village but after a day or two I think you would want to move on.
If you are looking for villages of England, rather than a specific area, then there are other counties a little more interesting and accessible. Essex does have charm but it is not as easy to find as some other areas.