Apparently Nirvana cycles in Westcott sell maps with lots of trails marked. Easy to find on Holmbury are Yoghurt Pots, Telegraph Road and Keep the Faith.
Yoghurt Pots – from the lookout on the top of the hill turn around and take the fire road on the right for about 75 yards, there is a sign on the right pointing to the trail which splits after a few yards, Doc at the Radar Station is to the left and will be very very wet, Yoghurt Pots is to the right.
Telegraph Road – At the bottom of Yoghurt Pots turn right, there is a green bench with a junction of several fire roads, from there you can see a set of telegraph poles, just follow these from right to left and you will end up at the Youth Hostel car park.
Keep the Faith crosses Telegraph Road after about a hundred yards from left to right.
There are many other trails round the Surrey Hills but most are trickier to explain how to get to.