It's on my doorstep and know a fair bit, but still couldn't tell you how to get place, I just put my compass head on.for the decent stuff u need someone with local knowledge.if you do go off piste just don't stick around drawing attention and carry on going.they do have land wardens and clampdowns but there mainly after illegal bikes.
I would take you up there, but I only get out every 2-3 months and it's usually a spur of the moment thing and only know day or 2 before.if I do plan to go out ill give u the heads up.
There's an annual charity bike ride up there end of the year, iv been on the last couple,there bit Thame but is a good day out and 80+ bikes that attend so bit of a social day aswell
Probably your best bet.. Have a looksie
http://www.ukgser.com/forums/showthr...y-offroad-2014