Ham Hill will provide you with almost two hours of cross country riding with lots of trails and varied terrain to explore.
At the main car park by the pub there are some lumps and bumps good for very short technical ups and downs.
Near the monument there are some longer open paths for blasting around. Once your finished this head South West ish from the pub, find your own way down the many tracks past the Gypsy camp which is pretty surreal. If you go East from the Pub along the obvious ridge there are a few DH tracks down the slope, short steep and mostly broken down but may be worth a look.
The trails roughly lie within the triangle made by Stoke Sub Hamden, Norton Sub Hamden and Montecute.
This is a good training/skills ride if you need something nearby.
Stoke Sub Hamden