East London:
Epping is very nice. Lovely detached houses with a country feel, pretty high street, forest...., tube
Wanstead, lovely detached houses by golf course, tube, decent high street
Teydon Bois, nice detached houses, tube.
(you'd get something lovely there for around 500K)
Southish, I love Chiwisk, you need more money than in East London, though, tube, nice high street with good restaurants.
If you want to be in commuterland Aylesbury is pretty, some parts of Bedfordshire, Hitchin in Herts...
When researching options outside of London I borrowed two excellent books from library: Escape from london and Guide to commuterland.