We've got to remember that BA is not just employing UK pilots, and therefore I can't see a day when it can't recruit sufficient numbers.
Like others have said, it's their train set and recruitment is not perfect with the odd lemon passing through. The problem BA have is that people rarely leave, and hence it's not such an issue if people are seeing the grass is not greener and actually moving to the sandpit/back to ezy etc.
There is an increasing awareness that BA isn't perfect (and never has been), but that's life.
I'd also say the flightdeck (in BA and elsewhere) has a broader cross section than 20 years ago, but that is wholly unscientific.