I think that the incoming flight paths to Heathrow have changed. I don’t think we had Heathrow flights directly over Forest Hill previously.
I contacted the Aviation Environment Federation http://www.aef.org.uk/
this was their response:
Dear Mr [Devonshire Forester]
Thank you for your query, which has been forwarded to me, and apologies for my delay in replying.
AEF is aware of flightpaths trials carried out by Heathrow in 2014, and that ever since, communities not previously affected by noise are now suffering, although Heathrow says that operations have reverted to pre-trial practices.
I am not sure about the exact routes of flightpaths, but I know that, while the number of flights to and from Heathrow has only increased marginally, some flightpaths are being used more intensively. Also, some of the aircraft being operated are heavier, and are noisier in comparison. This might account for the increased noise that your neighbour, and you, are experiencing.
In order to comply with the 1982 Civil Aviation Act, Heathrow Airport must consult with local authorities, airport users and interest groups who have an interest in its operations. Heathrow Airport Consultative Committee (HACC) is made up of several local authorities, and other interested parties, which serve as local representatives. The organisation called the Heathrow Association for the Control of Aircraft Noise (HACAN) is listed there, and it might be an idea to contact them to discuss what is being said in meetings about airspace use and noise nuisance (HACAN is likely to have more detailed knowledge of what is happening locally than I do). A full list of HACC representatives is here.
AirportWatch has produced a useful history and summary of an independent report into operations in and out of Heathrow, which you can read here. If you’d like to read the full report, you can do so here.
I am sorry that I can’t be of more immediate help to you, but I hope that the above will be of some use.
Community Outreach Manager
Aviation Environment Federation