Hmmh, odd.....
In all central and western boroughs, noise is substantially worse on westerlies, especially if living in Hamm+Fulham, Richmond, Barnes Ken+Chelsea and anywhere central, S of the river. It's even noticeable as far out as Islington/Tottenham.
I live in Hammersmith now, and when on easterlies, there is practically no noise whatsoever from Heathrow.
The newer types have definitely reduced the magnitude of the noise this past few years. Would say it's mainly Putney/Richmond and further west which really suffer on westerlies.
Footprint was worse in times gone past, esp. with the old Russian types, cargo 707's and the odd Concorde
. Ah, those were the days, when the approach was actually interesting to look at....