BA probably do not historically have any issues with age, per se.
Back in 1992 they sent a group of FLT ENGs to BAe Flying College, Prestwick to train for licence issue. This coincidenced with the 747-200 being replaced by the -400. A handful of Concorde guys as well.
I think the youngest we had was aged 28, and the oldest 44.
Once you get past 35 or so, it does become harder. A great deal more effort is required compared to when you were say 28 or less.
Having said that, if you have the aptitude, hand to eye coordination etc, age is probably no real barrier.
