Only to say that unless you sign up with a bike club and get to do a bit of Enduro or MX the number of places you can offroad is pretty limited in the SE and getting smaller all the time...thanks to Janit Schtweet Portah and all her rambling fanatics.
My brother helps run an off-road club and finds it more and more difficult to get venues for Enduros and stuff.
I haven't done any green laning for years but I do remember doing the entire length of the Ridgeway many years ago. Don't know what the current situation is but you probably couldn't do it now
Oh and get ready to have forearm pump and feel like you've just played a game against the all blacks after a hour or so