Hi,
I knew at least two Germans at XL flying the 737 one of whom was ex Air Berlin.
Have personally had a bad experience with Fly Globespan but others seem happy enough with it. And there are certainly plenty of Germans at Ryanair (I know that as a wave left Germania at the end of 2006!)
Don't think you will have any problems with the authorities - I made the trip in reverse and fly happily in Germany on a UK JAA licence.
For what it's worth, IMHO if you are making the move for personal reasons then all well and good, but I would be wary of moving for economic reasons. I suspect that AB have deeper pockets that Globespan and certainly XL. As for Ryan, who knows?
The UK economy is beginning what could be a steep downturn, after years of outperforming Germany. That said I'm also looking to leave Germania and considering a move back to the UK, so maybe we will bump into each other at an interview!
Good luck,
KT