Hmmm....
Greenhorn,
If you live in the UK but work in Germany I can understand your interest in joining a UK airline. The problem you would come up against is that it's a long time to command compared with other airlines in the UK. The bottom of BAs' huge seniority list with a below-par money-purchase pension scheme is not a great place to be at 40+ imho. Our rosters are determined by seniority and so is the fleet we fly on. Our retirement age is set to increase to 60 (we think!?), so any numbers I can get for you now will be nonsence in a few months.
If I were in your shoes I'd stay with the good job in Germany if I lived there. If I were in the UK at 40+ I would consider some of the other major airlines with quicker commands. I don't think the salary would be much different. Especially averaged out with a faster command. I guess with 5500+ hours you could apply virtually anywhere. I'm sorry if I've been teaching you to suck eggs.
Good luck.