I believe more a/c are vectored right hand downwind for rwy 10 i.e. over Dartford/Sidcup and my house! than left hand. Probably for spacing. however during quieter times like sat morning a/c arriving from the north seem more likely to get the shorter left hand join. I also wonder if there is some favoritism going on within thames radar as the BA planes seem to get the shorter option where as the likes of Euromanx and Scot allways nearly always fly over my place when 10 is in use! Although it obviously gives the controller more time to decend the a/c from 4000ft down to 2000ft. A/c fly lower over Sidcup than they used to be before the zone was enlarged ie. 2000ft instead of 2500ft.
