Kudlaty, I reckon you just have to appreciate that everyone at the final stages of these schemes is going to be pretty high calibre too, the vast majority with good degrees and experience. Plenty of people get knocked back at their first attempt, but are then successful the next year for the same or other schemes. Certainly never give up, all you can do is take it on the chin and work out how to improve. Criticising the process is completely pointless.
Divulging specific interview questions on an open forum strikes me as a very poor idea, particularly when you've just clearly identified yourself to the recruitment team who may well look at the forum.
I don't think they'd mind that you weren't British. The vast majority of their cadets are Irish, not British. Hopefully you didn't refer to Aer Lingus as a British airline, can't imagine it'd have gone down well!
Don't know if you're a guy or a girl, but with regard to having long hair; it's clearly not an issue if you're a girl. If you're a guy, you'd be nuts to turn up at an airline interview without having it short, neat and professional.
FlyVeryHigh's reflections are a pretty good example of how to approach getting knocked back.