...it should be noted that the average age of employees is greatly different between LHR crews and the rest ie LGW EASY VA etc who are bound to cost less as they are younger and have been with their respective companies for less time.
Rightly or wrongly, this is part of BA's problem. Too many crew have seen it as a "career" rather than a "job". BA is one of few companies where the majority of crew stay for the long term rather than a couple of years. While this has certain benefits to BA, they are likely outweighed by the negative of an inflated pay scale.