I just used USair to Gatwick and had no problems going over. Even got first class and was treated wonderful by all the crewmembers.
However, getting back was a bit of a heartbeat. I THOUGHT I was listed for the return flight. I was not. The ticket agent at Gatwick said since I didn't work for USair she could not allow me to jumpseat (Changed Oct 1??). However, she put me on the nonrev list and I was on the flight no problems.
She said that I would need to list in the future and call some TSA number for a background check? Not sure what that is about.
However, I had a great time. I left from PIT and I hear that is stoping soon. You should have see the line for Frankfurt...it was huge. What flights aren't full?
Good luck!