On a similar theme the car park for John Lewis near York introduced a 4 hour maximum stay a while back. The car park is for John Lewis, and also Marks & Spencer, Next, cafes, Costa etc. it is very easy to stay for 4 hours (not that I’d know personally, I’m in and out as fast as I can!)
It’s sneaky, in my opinion, in the way it blips up on a light board that you have entered, your reg, and that you have 4 hours. It’s gone in a flash as it captures the next car etc. Ian said there’s a board near the light board about 12’ off the ground setting out their t&c's. I didn’t spot it myself as I wasn’t staring at the sky, I was keeping an eye out for a parking space, as you would. We didn’t see any more signs nearer to the shops.
Many, many shoppers have been caught out and there is a Trip Advisor page specifically for that Shopping Centre with virtually all the posts regarding the Car Park and how people have been stung. Maybe it’s worth a quick check round if others have been punished in the same way your have been, lake_m, purely out of interest really. It’s a bummer when you are not a law breaking kind of person and try and keep to the rules and yet still end up getting stung.