AO
Some reasonable points, but it would need visibility of the recognition agreement, to see facilities for reps to clear it up. BA are bound by the agreement and I imagine that there would be a clause for them to serve notice on it, but not change it unilaterally. If the branch secretary position is full time, then that is what it is, but I do not know.
However, if this action can be proved to be targeting a union representative for his activities, it will automatically be unfair, rather than the range of reasonable responses test for non attendance.