If you do nothing, they will probably start court proceedings against you, and you will get assistance here with the process and a defence. In many cases, defended cases are discontinued before the claimant has to pay the court fee. But you need to post all relevant documents here if you want good advice, following the guidelines in the link above. If there was no space to park, they can’t charge you for parking, but you’ll have to follow the course for a few months whilst they try and intimidate you into paying them.