are the changes that are causing the proplem only on WW out of LHR.
No, the changes are affecting all fleets in terms of reduced manpower but seem to be causing the most problem on WW LHR. There are some differences around CSD work description and product reduction but the CSD/SCCM was already part of the service on short-haul and at LGW.
So in short, all crew on all fleets were balloted.