There has always been aircraft coming over at 4.30am since I moved to the South Dock area 10 years ago. You can check out on Teletext where they are coming from and their arrival time at Heathrow. It used to be Singapore or somewhere in the Far East. Whenever I am flying into Heathrow, I invariably look down and see Rainbow Quay, five minues before landing.
Have to admit that I am not bothered by the airplanes, it is more like the helicopters that drive me to distraction.