Came back from Orlando last year with Virgin and they couln't have been more friendly.
My examiner in Florida (I'd just done my PPL) gave me these tips for getting up to the flightdeck for my return journey:
I got the name of the Captain from the girl who checked me in. Whilst waiting to board I wrote him a quick note explaining why I'd been in Florida and that eventually I was hoping to become a commercial pilot and would be very grateful if I could come up and visit him sometime during the flight.
I made sure that I was first to board and as I got on I handed the note to one of the cabin crew (the most responsible and reliable looking one!) and asked him to pass it on to the Captain.
10 minutes later he came back and handed me my note with, as well as a correction of the spelling of his name, a note from the captain saying "come up straight away".
I ended up getting the jump seat for take off and landing, and he couldn't have been more friendly, giving me a running commentary of everything that was going on, whenever he wasn't too busy that is.
This approach worked for me, I hope it does for you - it's well worth it!!!