Going through the list of venues used in the British Hillclimb Championship:
Bo'ness - until recently it was an access road to a car park but has now been restored!!!
Dyrham Park - still the front drive to the National Trust property and would be easy to resurrect!
Great Auclum - no idea what state this place is in.
Pontypool Park - the roads are still there in the park!
Rest-and-be-Thankful - slowly been allowed to decay however there is a move afoot to get it back into operation; however it will need a heck of a lot of Armco!
Stapleford - I assume this is still there?
Westbrook Hay - front drive of a big house so should still be there!
The remaining venues are either still in use in the Championship or at club level. There are also a couple of the venues that are true road courses (Isle of Man) and they are naturally still there!