I too just discovered this thread. It seems there are enough people who were members of the BOAC Junior Jet Club that we could form a BOAC Senior Jet Club (though my late mother, a ruthless exterminator of 'clutter' threw the book out years ago). Fond memories of cockpit visits (always when the plane was flying straight and level) in the Comet 4B with BEA LHR - SVO and back and BOAC VC10s LHR - DEL with stops at (IIRC) Karachi Beirut and Rome. The VC10 didn't so much 'take off' as 'launch', like a rocket.
I'd love to see a modern aircraft glass cockpit, with sidesticks, in flight, but I can't see cockpit visits coming back any time soon, alas. Also, I think I'm a bit too old to be an unaccompanied minor.