I moved to the Surrey/sussex borders a year ago from SE London, in fact v close to Herne Hill and i love it. I could not have made the move even two years ago, I just wasn't ready. I had lived in London all of my life and couldn't see myself as a country girl. When DH and I met we lived in the City and gradually moved further and further out into the London suburbs with each preganacy.
The biggest pro that I haddn't reckoned for was the lack of fear - living in London you get used to locking everything up, preventing/preparing for burglery/mugging etc. Obviously we're still sensible and locking, but I can't tell you how lovely it is knowing you can pop to the shop without feeling threatened.
The schools are wonderful in the country and I know HH v.well and there is only one decent school in the area and another that people tell you is good, but actually isn't.
However it has taken me about a year to get used to it and to make new friends, it was v hard in the beginning. I do need to have London fix every now and then, but that's not difficult. DD commutes every day and hates the evenings, but likes the mornings. He works v long hours and thought he'd leave earlier and work on the train, but it hasn't happened like that.
The house prices here are about the same as where we moved from, but you can often get a great garden - ours is huge even though the house is fairly small.
No graffit, no grey, lots of green, no pollution only lovely smells, less dust.