Is the landowner still calling the police when he spots riders? I've not ridden there in 7-8 years but over the preceding 5 or 6 years spoke to the police a number of times and got (politely) told to sling my hook.
That said, mangrove was one of my favourite Surrey Hills trails of all time.
I think he means to the south of Coldhabour, possibly around here. There’s loads of stuff and it’s all a bit mad.
Dropped pin
Near Coldharbour Ln, Dorking RH4 3JW
https://goo.gl/maps/2gHzWNXt9SKukzGCA