I would suggest that Longhaul aircraft require about 8-9 crews per aircraft and shorthaul about 4-5 crews.
SEP requirement?
747 requires 12 crew (11 can be carried if no pax on upper deck).
767 requires 6 crew (if 6 crew carried pax number cannot exceed 251, otherwise 7 crew, which won't happen at BA since 767 EF is 247 pax and 767 WW is 199 pax).
777 requires 8 crew (ER requires 9 crew).