The NMC is a hidden gem. They let you pay a reduced entry fee to see the Heath Robinson machine and Colossus (which is what everyone visiting Bletchley Park wants to see). I've always thought that was a shame because so many people don't get to see the rest of the museum (which is mad, and brilliant).
But they also have a BBC Micro lab, complete with a Domesday Disc setup. Which you can play with. It's surprisingly usable.