Great photos
@Scaleyback
I have a mid 80s(?) Dawes Shadow that I bought in almost new condition, it had spent its entire life in a garage. It superficially meets the criteria but they might not let me in because on closer examination it's clear that I've fitted wimpy lower modern gearing. And ditched the original steel rimmed wheels. (I also accidentally ran one of them over with my car so I can't return it to its original state)
I think if I did want to go on such an event I think I'd have to get into the spirit and try to prepare something a bit more strictly period correct.
In my teens I had a handlebar mounted water bottle similar to the ones pictured. I made the bracket myself from jubilee clips and a coathanger.