Luigi.. Large jet aircraft don't come down to 50 ft in the dark over an unlit civil aerodrome! Where do people dream up this nonsense?? In any event, ATC would know almost certainly about any movements (ATC in that area is provided from the London Terminal Control at Swanwick).
Police helicopters operate throughout the night and may well fly very low. Perhaps one of those was seen/heard??
I just read Luigi's profile - I can't believe it!!!!!!!!!!!!!!!!!!!!!!!