I think the bike centre does guided rides for about £20. Or there's the uplift service if you just want the mini DH stuff.
If you Google the "Fountain Inn" , they have a couple of routes on their website (but beware, Lawnmower has probably disappeared).
Otherwise, you could head to Mile End (small village, you'll find it on the map) and head eastwards and downwards from there and you'll find some fun stuff. Also from Worcester Lodge (see OS map). And, if you go south of Speech House Road you might find the likes of Dowies...
I've found most of the stuff I know about from riding around the west edge of the woods in those sections and looking for trails heading back east.
The old Enduro trail (small "E" if you know what I mean) is now mostly tarmaced over by the Verderers.