Had a parking ticket there earlier this year.....although slightly different for me in as much as the car i was using was a rental car, and i did try to 'phone the number at 5 a.m. to pay, oddly the line didn't work, hence couldn't pay, and had to go off on a few days flying and leave the car parked without paying !.
First i new of the parking fine was when the car rental company sent me a letter advising of the £150 penalty (reduced to £75 if paid within 14 days), along with their "admin" charge of approx. £36. I was slightly irritated, and drafted a quick letter off to the company concerned about the circumstances leading to the fine of £150, and in fairness they then invalidated the fine. Took a little while longer to get back the £36 admin. fee from the car rental company mind !! lol.
Might be worth a letter in summary to the company concerned ? oh, think the company concerned use ANPR to issue fines to cars parked in contravention...not sure what time period they use as a "cut off" to issue offending cars ?