Earlier in the summer I hired a car to take on the ferry to France. We sailed from Plymouth and 6-7 hours to kill before sailing and went into a multi-storey carpark signposted 'parking for the Mayflower'.
It was utterly rammed - we basically sat in there for the best part of an hour bumper to bumper. We got up to the top - there were no spaces whatsoever. I saw one person in front get parked in that time. Because I could see people at the pay machines I thought they were leaving - ime you pay at machines on leaving in MSs, so I made the mistake of going round again. At one point, we did find a space but it was ridiculously tight and, being in rental car a lot bigger than my own car, I had to give up. There were people right up behind me - it was horrible. At that point we'd been in the carpark about 40 minutes and it was beginning to feel like our whole holiday was going to be spent in there!
We then found a space in the open air in front of the water where you had to pay by phone, which I did and we stayed there for four hours.
Yesterday a fine came through via the rental company for the MS carpark I never actually parked in - they obviously have cameras to catch you going in and out. Now I have no proof that I never parked in there, except. looking at my phone records I have the call and text for the other carpark, and I'm pretty sure it's the same company - both have Bournemouth phone numbers. So why would I go in somewhere for 50 minutes, fail to pay then repark just outside for 4 hours and pay! AIBU to think they will accept that?
Fwiw the first carpark was an utter shithole imo. It should have displayed a 'full' sign - if they can afford the technology to record people going in and out, then surely they could do that as carparks round here do. We wasted nearly an hour in there, and it was hellish. Also it was pay and wanky display! Who does that now? If it had been a 'normal' carpark' with a barrier that dispenses a card this wouldn't have happened as I would have had to get assistance to get out at the time. Also the spaces were ridiculous. I know I could have probably parked had I tried again, but the only other person I saw parking had to be guided in by passengers - I only had small children with me.
I f I have to pay it will be £140 - because I will contest which means I won't get the 'cheap' £50 fine, 
and the rental company charge £40 admin fee for transferring it to my name which is refunded if I win an appeal. AIBU to think I surely won't end up paying that?