Well, I got one decent shot from just outside the entrance to the Oxford Street tube station. That's when I regretted not carrying my DSLR with me this time. I'll try to get better pictures tomorrow.
And I found out that the balls of light (just above the bus) react to the pedestrians/traffic/sunlight/wind and change colour/brightness. Good thing I did because the sequence/timing of colour changes was really bugging me when I was standing there waiting for the No 15 to show up all these mornings :).