SW London - where exactly? Sutton, Esher, Surbiton? It's very difficult in those area because inbound aircraft will be under radar control and there is no restriction on where they can be directed. Departing aircraft, which are noisier during the climb out, do follow very accurate noise routes but when Heathrow is landing towards the east you will see many outbounds right over those areas. Possibly the quietest areas, if you must live close to Heathrow, are immediately south and north of the airfield.....
The further out you go the better off you'll be....