I’m of a mind to challenge as l9ng as I can still pay the discounted rate which i think can.
It's impossible to say as you've redacted the date of the PCN, contrary to
the guidance. If you're going to make representations, I'd suggest you do so sooner rather than later, and that you do so via the council website (keep a screenshot of the confirmation page). The discount will be reoffered if you make representations during the discount period.
The criminal offence the poster mentioned was that you 'appeared' to have stopped with your front over/across the stop line at the traffic lights from the video. It maybe though from the camera angles this may not have been the case at all and you did indeed stop short.
I really wouldn't worry about it, the police does not take action for such de-minimis offences anyway, and even if they wanted to the 14 day deadline for a NIP to be served expired many, many weeks ago.