rog747 thank you for your post. If you google IAS it will show that this is not an independent service after all ! The IAS is owned by the parking companies and apparently any appeals to the IAS are futile as they will never rule against the parking companies.
This is from the IAS website:
The IAS is administered by the International Parking Community (IPC). The IPC is a trade body representing the interests of private parking operators.
And this is a recent thread from Moneysavings Expert:
https://forums.moneysavingexpert.com/sh ... ?t=5962444
According to this thread UK CPM are the most litigious of operators. According to other threads it is safe to ignore the PCN.
It seems clear that the signage changing the maximum 10 minute drop off time was not clear and not sufficient given so many of us had the same issue ? Really not sure what to do next. I am not sure I have the nerve not to pay !