The private car parking firms in the UK are a nightmare.
We got stung whilst on holiday over there in Cornwall this summer.
Didn't appeal it as the car park firm don't recognise the ombudsman, you go through some private appeals firm.
I'm sure they target rental cars, as you generally have a month to pay at the reduced rate, then it goes up to 150 of your english pounds. Once the rental car firm get the fine from the car parking company and they then get hold of you, the month has generally gone past, plus you pay an admin fee to the hire car firm.
The car parking firm reckon we didn't pay; I know we did but who keeps hold of their old tickets after a holiday abroad. You get rid of them when you clean out the hire car.
I argued the toss re the dates and amount of time it took to get the ticket. They re issued and I paid the 20 pounds fee just to get it over with. Then got another email from the car parking firm saying you haven't paid so owe is 150. I sent them my details and payment details and told them that I didn't expect to hear from them again, and havent.
Try parkipedia - they may have some info for you.
good luck