I'd have to agree with BerksFlyer, I don't think many of the younger applicants have any intentions of leaving BA if they gain employment as a pilot.
As an applicant of the younger variety myself, if I were to gain a career (and that expression being key; "career") I would never consider leaving; I mean where else would I go?
I am accustomed to western life in the UK, and as modern as the middle east and far east are becoming, it's not an attraction to me. Also, from what I've gathered, life in the Americas as a pilot isn't as great as in Europe.
I know a little about BA as an employer and from my interpretations they provide a very stable, secure and rewarding career.
Unless you have no responsibilities and live a hedonist lifestyle, you've no reason to leave. Besides, if did have all those traits in your personality, BA wouldn't even consider employing you anyway.