Well done for going out for a look!
barnsdale tunnel is an easy one (do a search on here) no walls to climb no wellies needed and about 1200 yards long may be quite a ride for you (nearest town is pontefract)
Dave, did you start the old flickr group?
Crigglestone is much easier than it has been as the centre section of razor fencing has been removed.
Even so, it's still HUGE