I recently visited Bletchley Park, near Milton Keynes in UK. ( http://www.bletchleypark.org.uk ). This is the "National Code Centre" - the site where the German Enigma code was broken in World War 2. This work was secret for a long time and the story is only now being told
It is a facinating place and must be visited if you have any interest in history, radio or computers. It also houses other related exhibits, such as the museum of computing with the rebuilt Colossus computer. There is one hut stuffed full of vintage radios, including some of the WW2 'Spy' sets. There is a permanent amateur radio station, but it was closed on the day of my visit.
I took the conducted tour - which is free. Peter was our guide and he is an absolute mine of facinating information.
The only thing that let the place down was the catering, which was awful, and there is no alternative near by so do take sandwiches!
Entrance was £10, which allows unlimited visits for a year. I only allowed 3-4 hours for my visit, which was nowhere near enough so I will be going back.