This situation seems to happen at LPL and MAN - the two airports I travel through most often - on a regular basis. The attitude and general slowness of the BA staff does leave a sour taste in the mouth, particularly as I will have inevitably been welcomed into my foreign destination with a smile on the way out. The lengthy queues for passport control also seem to be a uniquely British phenomenon, I don't recall queuing as long anywhere else.
Although I would point out that it isn't just BA staff at airports - the sheer miserableness of customs/BA at Portsmouth ferryport has to be seen to be believed.