VC10 Man
It may seem ironic, that even with the excellent bmi facility at EMA, bmibaby 737s were sent to Sofia to have major servicing done by Lufthansa Technic.
EMA was only used for day to day line sevicing.
As TSR2 says, it's all down to cost.
You are right though, the 737s are a credit to EMA, with the two (G-OBMP and G-ODSK) which have been with British Midland from new being the best two in the fleet.