+1
Sorry, OP, but as cp8759 says, the video shows you as totally bang-to-rights. You entered the YBJ when there was no room on the other side of the YBJ for your car to drive into. You were also already stopped in the box when the pedestrian appeared.
BTW, your text shows that you are under a misapprehension about the restrictions imposed by a YBJ.
I could not estimate there would be a standstill traffic before my car right after the yellow box, giving that it's a clear green light.
All the traffic light going green means is you can proceed if you can pass over the box without stopping. The video shows that you would have clearly seen before driving forward that there was no room.
Sorry if this isn't what wanted to hear, but we deal in reality on this forum, and the plain fact is that the discount is your best option. Certainly you would lose at London Tribunals and have to pay £130.