So they do open up from time to time then???
The Science Museum collection at Wroughton has very occasional Open Days, I think the 2005 date that HD referred to was one of the last ones, which I also attended.
They have a big problem in that one of their hangars is technically unsafe and so for Health & Safety reasons is never opened up to the public. It's the one with the Trident, Comet and other assorted aircraft.
See
http://www.pprune.org/aviation-histo...wroughton.html