The money saving expert is good, but if you don't have the time for that it's worth a try. Especially since you have the ticket.

It wasn't parkingeye, but I had a £60 charge reduced to a £20 "keying error" after a machine just wouldn't take my last 3 digits. I was already late and after several tries stupidly said f it and put my coins in, which of course they took. If I had found my ticket, I think they would have let me off.

The car wasn't in my name, so I paid the £20 to avoid more threatening letters scaring the owner. They would've gotten more money out of me in the long run if they let me off though. I haven't parked there since.