It's not a fine but by entering the car park & deciding to park there you entered into a contract with the parking company so as long as the terms & conditions were correctly displayed in accordance with POFA you are liable to pay the charge.
What are the circumstances (overstay/not in bay/other?)
I had something similar. A fine for overstaying the 2-hour limit. However, I was unable to confirm who was driving my car (since DCs refused to admit) and wrote to the company (or did it online) so the company was therefore unable to take the matter further.
It’s an urban myth that only councils can fine you. Have a look around the BBC for a fairly recent story about a woman going bankrupt for believing such...
BUT were you a genuine Morrisons customer? Got a receipt? I work in a retailer-linked industry, and they’re usually concerned with their customers experience I.e. not having a negative one... so, do have a go at nicely asking their customer services to get it cancelled, but don’t delay paying as it’ll hurt even more if you get additional charges. And bear in mind it may well not be Morrisons in control of the car park and the parking controls, but may be a landlord.
It pissed me off royally [topical], since £118 was spent in said supermarket yet apparently one is not allowed to overstep the parking mark. None of us has shopped in Sainsbury's since that date. I wrote to complain and got nothing back. So fuck you Sainsbury's!
I appealed mine from a similar company and evenues then it went on forever. I was still getting letter a year later . Even though I won my appeal because the company basically sent me a photo of someone elses car instead of mine (I pleaded major data protection breach) I recieved a letter from a solicitor regarding it.
I then had to ring solicitors to point out I'd successfully won my case.