alt Hacker Newsthat's what i was describing! :) it's on the bletchley site (they share a parking lot) and was where tony sale and friends rebuilt the colossus.
although i just looked. critically they have different ticket offices. it was a long time ago! either way, worth a visit of both and they make up an excellent way to spend a day.
It's on the same site but there is some institutional nonsense that means getting onto the Bletchley site doesn't guarantee access to the NMoC, which is only open on Tuesday, Thursday, Saturday and Sunday.
Don't ask me how I know...