Hi Dougie B
As others have mentioned there is a lot of info on the net regarding these parking scammers check if they are members of an appeals body such as popla etc.
All car parks should have a grace period especially for disabled and single parents with children.
It would be intresrting to know if the car park was part of a reatial park or store and how long over the permitted allowed time where you parked.
If it was a retial park/store contact the manager of the establishement direct ask about grace periods etc.
had loads of these and never paid a penny dont be bullied into paying as there are not parking fines but a parking invioce.