I just came back from a business trip to BKK on BA9/10. The plane was fully booked both ways, so I don’t understand roumors to downsize the aircraft to a 777. If BA is to change to a dayflight, they will definately loose a lot of customers. Overnight flights are the only bonus for longhaul in C/F you can get. Everything else is a waste of time. The only desirable change on the BKK route would be an earlier departure from LHR, to allow for an easier adjustment to the time change.
BA15/16 to SIN was also downgraded to a 777. The result are overbooked flights, especially after QF dropping the LHR-SIN route. Sometimes BA-decisions are simply not understandable!