Unfortunately for the PCCC you are going to have to grow your membership base from existing Cabin Crew only as the new Mixed Fleet Crew have no entitlement to union membership nor have they any entitlement to collective bargaining
Wrong, in the UK every employee is entitled to be a member of a trade union. If represented by a trade union a member will be represented through collective bargaining once the employer recognises the union through voluntary or statutory means. At least one of the offers put to the cabin crew included recognition of MF crew as a bargaining group to be represented by UNITE so I would imagine that would be BA's preference going forward.