The main legislation in this area is "THE ALTERNATIVE DISPUTE RESOLUTION FOR CONSUMER DISPUTES (COMPETENT AUTHORITIES AND INFORMATION) REGULATIONS 2015" It's a mouthful but essentially it is a means to keep any disputes out of the courts and getting them settled beforehand. Parking companies dislike not being able to threaten people so are careful to bounce people out of the very narrow and self-imposed limits they lay down - in breach of the legislation. For example the legislation says a consumer can have 365 days to appeal but the parking companies attempt to limit it to 28 days (British Parking Association) and 21 days (Independent Parking Committee)