1) Many years ago, on Christmas days, Heathrow would open up its airspace and runways for light aircraft to land free of charge.
Many years ago, Wycombe-based club aircraft (from what was the BA Flying Club, and maybe others) certainly did use to fly approaches at Heathrow on Christmas Day.
Don't think they landed, but it was before my time flying with one of clubs there, so may have that wrong.