Ryanair
i work for ryanair at stansted airport and i too have had a few jump seat flights not just from ryanair but first choice and flyglobespan but that is becasue i showed my Airside ID which help's very much.
however the best way to get a cockpit flight or visit is to take a look around the forums and try and find a airline pilot and try and become friends. he or she may let you come up if you book a flight with the airline and your on his flight (thats how i got my first flight deck ride in a A319 Easyjet and i had found the captain from the airliners section of PPRUNE)
so just give a few things a try they do still happen even after 9/11 its just luck i guess
good luck