Not wishing to put a damper on things, but I do have to wonder how this "recognition" has apparently come about.
Some brief details of the ins-and-outs are here:
Trade union recognition : Directgov - Employment
GMB are in fact already recognised in some areas of BA:
gmbinba.org – For GMB members in British Airways – Your Trade Union Voice
Just a thought .... who represents BMI CC? Could it be something to do with that?
If this is really happening, might it eventually lead to the de-recognition of bassa?