Just to add balance to the doom mongers,
Most of the doom and gloom comes from long established BA pilots, who haven't experienced the outside world for a long time. In my role I meet a lot of fresh, recent joiners who are extremely aware that the 'unsustainable' roster pattern is significantly better than the one they have just left. Also once your roster is published its set in stone unless you agree to a change, no last minute shenanigans.
It's human nature that the people with the biggest gripes shout the loudest while those just getting on with it keep quiet. Yes you'll have to work hard in BA, but where don't you? Yes the seniority means you'll have less control initially but more later and we've all been there. I can count on one hand the number of days off I've 'needed' but failed to achieve, get good at using bidline and you'll usually achieve that one day. I've never been Gatwick based but have friends that are, they're not unhappy.
Come on in, the water's lovely!
LD