In reply to stucknortherner:
not had a ticket, but it's definitely time restricted at Morrisons FW. This will be to stop people parking there for a week while they take the train down south. As it's in Scotland, the rules are slightly different. My friend had a similar episode with Lidl in Glasgow.
When a ticket is issued by a private land owner, it is a civil, rather than criminal matter. There are a few things you can check -
1. was it appropriately signposted that there are restrictions? could a person reasonably claim they were not aware?
2. Is the charge they are trying to Levy too high? (remember they can easily justify this with overheads - private security employed to police - cost of signs, CCTV cameras and reg plate recog systems etc). They would easily be able to come up with a justifiable bill for £100 for example).
What they are doing, in essence, is proposing that they take you to court to make a civil claim for compensation. They will say "pay the (fake) overheads and we'll drop the case".
If you ignore it, they probably wont want to pay to go to court, even if they can recover the legal costs from you if you don't win, but do you really want to risk that? It could also have an impact on your credit rating if they pass the bill on to a debt recovery company. There are companies that specialise in recovery of parking fines.
They're all a shower of Sh@*ts, but I know if I got a private carpark fine I'd definitely suck it up and pay it ASAP, hoping to get an early payment discount.