Fortunately the small Memorial to the Polish Cryptographers who are the reason this was worth attempting is outside so we could visit that, about a third of the team were Polish (we hired away some subcontractors from a Polish firm, and then we were in turn bought by Experian) so visiting this memorial was a key part of our intent.
Also IIRC at that time the Bombe was still not in TNMOC, and Colossus was in a separate building so you could see it, but the rest of TNMOC was closed.
I've also seen an even earlier incarnation of TNMOC when I was younger, just basically a room heaped with obsolete computer gear, with some nerds who know roughly what it is but aren't equipped to properly exhibit or explain it. I remember they'd set up some video game consoles, something like the original Sonic The Hedgehog maybe, because they wanted children to have some positive impression, obviously a kitchen appliance sized "disk drive" doesn't mean anything to a child, but it's obvious Sonic is a game even if you're used to much flashier graphics.