Why not go to the large and good Dunstable Downs hamfest in the morning of
17th 20th May, and then TNMoC (or Bletchley Park if you insist) in the afternoon? I will.
The National Museum of Computing is one of the few museums where the attendants really know about the exhibits, e.g. they are more than happy to whip out the circuit diagrams and discuss them with you. *Highly* recommended!
You can also see he world's oldest operating computer (WITCH), Colussus, and horrify yourself that your treasured childhood possessions are now museum pieces
http://www.ddrcbootsale.org/http://www.tnmoc.org/