Suspected thread hijack in progress...
Mikeoscar, you might want to check this out:
http://www.caa.co.uk/docs/33/FOD201021.pdf
FODCOM 21/10 | Publications | About the CAA
Unless you are fully licenced, LPC'd, OPC'd, with security courses and fully enrolled employee of a company, I'm afraid you're out of luck. PA's on board a commercial operation are now a no no in the eyes of the CAA.
However if you can get yourself known at a local GA airport with some based King Airs etc you may get a ride in a privately owned twin of some kind. You will not be part of the crew from a legal perspective but if you can get the experience it will be well worth it, especially if you become a regular passenger up front.