Not only do we get the Heathrow bound flights, we also get the city airport bound flights that do an about turn over Brockley/Peckham. I only know this as I have the Radar24 app installed on my ipad, and was sitting in my hot tub last night tracking where they were coming from/going to.
I always thought airplanes had to have a minimum of one mile between them. They come much closer than that very frequently...