Thank you for this tip: I saw your comment this morning and went today (am visiting London). Great stuff. Not as much vintage “modern” computing as the Computer History Museum in Mountain View but lots of amazing things, and of course lots about the Enigma and code breaking.
It has so many things to look and interact with.
Most notably the Colossus, Bombe, Acorn computers and BBC micros.
If you are visiting as a tourist it's not too hard to get there from central London by train or car.