Close?....Brize Norton, of course - if you've ever tried calling them for a radar service as a GA operator, you'd know why - they were bad enough when trying to get a zone crossing in a military transport or fast jet, but I didn't know I was born then. Also, their Zone is spreading like a cancer into the (what used to be) free southern English airspace.
Open?.....Abingdon and Thorney Island - had some great times at both places.
A