Hidden gem areas in or around London

[GlobalTravellerbutespeciallyBognor]

Are there any areas you know of that you think are lovely but not on everyone’s radar yet? (Please don’t just put where you live!)
Thank you for any insights.

I think it's getting more well known now but Highams Park, E4. There was a recent newspaper article- in the Times maybe?- about it being the best place to live in London (or something like that).