I'm cabin crew and have worked with a couple of pilots in the cabin. Both (femal - not that it has any bearing) were fab - very organised, focussed on safety, and very chatty with the pax. One has gone to fly with GB, the other has left and flies helicopters in her spare time. I think there is a certain personality type that works well in the cabin, but I don't think that flight deck crew are immune from being sociable (too many sore heads on trips have proven that!) Certainly in a small airline like mine, (don't know about BA), flying down the back certainly (if you play the game well) gets you familiar with the top brass, and allows you to develop good connections when recruitment time comes up.
Best of luck