Shoreham has struggled with parking control for more years than I can remember.
For many years, you could park anywhere. It kind of worked, except that the place was exploited as a free car park for car pools (car sharing, whereby four people drive in, park 3 cars for the day, and then continue to the workplace in the 4th car).
Then Northbrook College got going and this soaked up a lot of parking, making the old system unworkable. Students have too much money these days
Today, based pilots and employees can get permits, which entitle them to specific car parks. Visitors have to pay up on a meter. This seems to control the traffic, though the restaurant business has gone way down AFAICT.
The present £90 fine size is way OTT, although you do get a £90 ticket at any number of streets in Brighton.