If I could just point out that "BALPA" consists of individual company councils. If there is something you are unhappy with, you need to be working through your company councils.
Nobody can expect other airline councils to be improving T&C's in your company. Is it strange to expect the BA BALPA company council to be looking out for BA pilots?
As far as I know, the central facilities at BALPA are there for all company councils to use.
In this particular case, BALPA is fighting for holiday pay for all UK pilots.
(In the interests of fairness, I do work for BA and am an ex-BALPA rep.)