my son come back from the gym with a parking ticket,

I wonder how we can appeal, these are the conditions at the time,

Ely ( cambridgeshire ) has free parking in ALL its public car parks,

Son attended at Sports Centre / Gym Car park, which was full,
Many people park there with NO intention of using the gym and walk into town, car park is for sport centre users only.
No spaces, so son parked on a grass verge, and mentioned this to gym reception and they said should be ok, we know you are a regular user of the gym,

Ticket was for :

Parking in a prohibited area - they are no warning sign saying cant park on grass etc
parking outside a bay or across 2 bays

Son was not obstructing any walkway or any other vehicles what so ever,

Seems very steep to fine £60 for a FREE car park,

any advice?