Hello, I hope you are well. My name is***** am a solicitor advocate and I will be assisting you with your question today. I am very sorry to hear of the problem you are experiencing and I will do my best to help you with this matter.
Sorry hear what has happened.
If the park was closed and security was on site to stop people coming on, then clearly it must be that the company site owner must know or even be responsible for the damage.
However, if they are not accepting responsibility, then your only action is to go via your insurance company. They should then settle your claim, and may in turn sue the park if it is shown they were responsible.
If toy can prove that damage has been caused to your van by the company, the n you may actually be able to report that as criminal damage to the police.
Criminal dams is not just intentional damage but also reckless actions that cause damage.
Inform the park of that if you think theey are liable, they may decide to think twice.