The Asian airlines tackle this problem by using their 744's and other long haul aircraft within Asia for a flight or 2 before turning them around back to Europe. I would assume that BA has them go off to NY and back in some kind of rotation so as to not have them sit on the ground to long. I remember reading somewhere that BA uses a 744 16-20 hours per day on average.

I would also suspect that there have been odd orphan flights of the new Club beds which are unannounced when there are aircraft rotations.

Interesting enough, US carriers often rotate their aircraft by having them fly to/from the west coast from the east coast in order to greater utilize the aircraft.