Shuttle used to be the preserve of BA LHR routes to MAN,GLA,EDI & BFS(when BA used to do that route).It was Speedbird on the other LHR domestics(to NCL,ABZ)& on all BA mainline out of LGW.
From last winter(if i remember)it was changed for some reason to take into account ALL BA domestic flights out of LHR & LGW - to MAN,NCL,EDI,GLA & ABZ.
British is indeed for BA Regional flights.
Speedbird for long haul(possibly European flights as well??)