I don't mean to be "that person" but I'm local to the area and highly recommend you don't visit there. It's still an active airfield, might not seem it but it is. There are signs up to say no entry, but like Mookster says, it isn't exactly challenging off the public footpaths. You could get away with being on there, it's rare that people are caught but I wouldn't like to risk that with a military airfield.