Maybe this is hair-splitting, but it could (and probably will) be argued that just as an employee has a right to withdraw labour, an employer has an equal right to withdraw perks. The pinhead we are trying to balance an infinite number of angels on is whether BA in removing staff travel perks from those who went on strike were acting in a manner calculated to prevent staff from exercising the right to strike. Since the removal of the perk was after the individual had gone on strike, it could be argued that the act of removal did not prevent the individual from taking strike action but was consequential.
Unite will need to establish that the threat of removing staff travel was not only intended to prevent staff from going on strike but also was the sole reason that some staff chose not to go on strike. Going to be quite a tall order given the abuse heaped by BASSA on those who did work normally.