Oxfordshire has a cool dh riding posse with flippin’ good paths one of these can be found at Russells Water nr Henley which is short sharp technical blast.
There are also some real good fast stony downhills to be found in the BBONT woods area.
If playriding is your thind there are some decent jumps at Nettlebed.
Also check out the mad Hollandridge downhill at Stonor as seen on Chainspotting. Seeyou out on the trails.