Thanks to a couple of very kind crews with Dan-Air and GB Airways I was lucky enough to enjoy several landings at the sharp-end a decade or so ago, and would dearly love to do some more - but I have to agree with Rainboe and Oldlag that in this day and age it aint on.
Don't think we chatted too much, but both Captains gave me a briefing of the approach we were about to fly and a quick "Cooks Tour" of the panel. Much appreciated!
Regarding the vetting, I was travelling with a friend who worked for Dan-Air, and whose wife worked for GB which seemed enough of a reference in those days!