I used to drive past it almost every day. Band of Brothers was partly filmed at Leavesden, but a lot was filmed over at the old BAE grounds in Hatfield.
The first film to be made there was GoldenEye. I remember seeing the set for the statue on a tank sequence built there. The airport part was used in external shots for the film - including adding it to a matte of a distance shot where it was curiously on a cliff’s edge somewhere in Russia.
I still remember the Sleepy Hollow windmill there, which was quite striking.
http://en.wikipedia.org/wiki/Leavesden_Studios