NB: Worth checking (I think I've managed to get this wrong twice so far!) whether both the Bletchley Park museum and the National Museum of Computing are open, since their opening times don't always overlap well.
We actually took a day trip with a team I had at a previous employer to see the NMC, but turned out it was closed, the Bletchley Park museum is cool, and we needed to see the plaque you mentioned because that team had several Polish people who were integral to our success (hi Monika if you're reading!), but we specifically intended to look at the NMC because it's a team of software engineers, so that was a little disappointing.
A Bombe doesn't exactly "decrypt" messages. What happens is the bombes are eliminating impossible settings. So you put in a message, and a guess about part of what it says, and the Bombe tries keys, rather like brute forcing a password. "ABCDE, No. ABCED, No, ABDEC, No" and so on. The way Enigma works makes it possible to rule out some keys if you guessed part of the message. When it can't eliminate a key, the machine stops, "CABDE... Maybe". A team of mostly women would try these "stops". Maybe CABDE produces gibberish, the machine is set running again, next is "DEABC" and this produces a message that looks like human text, send it to the German translators in another hut. [ The actual keys in Enigma are not five ASCII letters ]