I think your numbers are more than slightly out! BA's pilot strength is around 3000. A great many more than just those who reach 55 leave each year, for a variety of reasons; their declared pilot requirement for 2005 was (IIRC) about 140. BMI has around 600-700 pilots, who (like most UK airlines) retire - or at least leave the LHS - at 60. I'm not aware how many they need this year, but I'd guess 50+. Virgin have 650 pilots; our requirement for 2005/6/7 is around 80 per year (though we are expanding).
OAT's share of the market is significant, but is far from being a majority supplier!
Scroggs