Nice photos but we need to see the PCN, please. Only redact name and address.
I have to say it doesn't look good at first glance, but let's see the PCN. Cases have been won many times on the council, (or TfL), not following the legal enforcement process correctly. This can make the PCN void.
If you'd stopped on double-yellow lines nearby to let people get out, you could have claimed the board/alight passengers exemption.