Can't see any issues with the video footage, it's an open and shut case in that respect!
The date on the PCN is almost three months after the date of the contravention. Is the vehicle leased, hired, or any other reason why this might be? Normally the council only gets 28 days to serve it.
The PCN has a very specific timing for the contravention, including the seconds. Technically the offence occurs when the driver causes the vehicle to enter the box junction in the first place which is a few seconds earlier than stated - but I don't think this would be a strong point of appeal!