Any issues with the signage?
https://www.youtube.com/watch?v=rGa_oc1ZSNgThree vehicles going through in 20 seconds might indicate there's an issue with them, but you'd have to go back and check. I wonder if there were any roadworks / diversion signs in the area?
If the amount on the website goes up to £70 before midnight on 29 April then you'll have a valid ground to appeal, namely that the penalty demanded exceeds the amount due by law. However you would need a timed / dated screenshot, this is easily done by opening the council website and then the website
https://time.is/ in another window and screenshotting the whole thing.
I'll get hold of the traffic order.