i had some pax travelling from SIN to Australia who said that they had previously flown BA a couple of times and just said "well, BA are BA, awfull every time, nothing new". I have never flown BA so i can't comment on it, but these are just comments passed on from what a passenger had to say. I have travelled SIA before and found them nothing flash.
At the end of the day in companies so big, you are bound to have some bad apples around, that's just the way it is. It's just unfortunate that these bad apples stick in people's memories more than the good apples! People are going to remember bad service more than they remember good service.
Oz