BA will do fine, but only as a London (LHR) airline, there will be nothing 'British' about it. The foreign long/short haul carriers are taking the traffic directly from the so-called 'Regional' airports like MAN, as travellers choose that instead of BA via LHR.
Interestingly JET2 have just pushed BA off the MAN-AMS after 50 years, and last month BA stopped MAN-CPH when Maersk joined Scandinavian on the route, so i'm not exactly convinced about their competetive instinct. I expect that the Open Skies agreement and LHR access for transatlantic slots will be the big issue for BA.