OVNI. Reino Unido

Fulham, London walking to a cafe. Airspace is busy but on this occasion I looked at and saw a star like object about 7 aircraft widths to the left of the passenger aircraft. Then noticed several lights to the right of the aircraft as I looked up: about 7, 12 and 15 aircraft widths to the right. They followed the aircraft and continued to follow it, keeping the same relative distance, as it banked gently toward a more northerly path. At first I thought they were balloons reflecting bright sunlight - I've seen some rarely - but thes lights remained at a constant speed, had a smooth direction and all turned relative to each other, and at same distance from each other. Also, they seems to emit a constant light and not reflect it, whereas balloons change intensity as they tilt relative to me/observer and the sun. The aircraft wasn't landing at a London airport, those are Only a few thousand feet above observer-point and the aircraft had a vapour trail and I should imagine it was over 15-20,000 ft above me. Aircraft and light were obscured by city housing then.