Thanks for all the responses folks, very much appreciated.
I knew it would be a long shot but had no idea what the laws/rules were governing this kind of thing. As a qualified commercial pilot myself it is something that we were prohibited by law from granting after 9/11, much to the chargrin of the great majority of aircrew flying around the world. Before 9/11 it was always welcome and indeed, as a young flyer I had many a jumpseat for the landing and take off on numerous airline trips across the world which inspired me later to follow a career in the skies.
It surprises me that there are no such laws prohibiting members of the public from riding in the train cabins too, and is purely down to TOC operations guidelines. I have a friend who drives for NXEA and he says it is very hard to arrange at his company although he is still trying to butter up the right manager on the right day!
Anyway, as far as my journey at the weekend goes, I shall surfice with just a chat (hopefully) with a driver (if I spot one) and enjoy the privilages of the buffet cart instead!
Kind regards,
Baldieman.
PS: Regarding flight deck visits, most airlines will welcome you to the flight deck before engine start up or (more likely) after engine shutdown. The law states no unauthorised person on the FD whilst engines are running. Hope this helps for interested people here.