However my biggest surprise so far as I've deduced from some of the posts is that BA don't do fixed links....
Is there a reason for this or BA is too big for that to work.
Once you have large numbers of crew switching a/c it makes sense to increase the amount of "down time" between flights. That way the crew can be waiting for the inbound aircraft and the next flights won't be delayed due to out of position crew.
As to why changing aircraft is necessary in the first place, no idea.... Surely BA's schedule is fixed enough (and a/c turnarounds short enough) for the aircraft, pilots and cabin crew to all do more or less the same? Just think of the savings in rostering complexity and associated costs...