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 to hear what has happened.
If the van is on their property, then there is little you can do about that. It is no more a fire risk then a car being parked there.
However, if there is indeed a restrictive covenant then that does change matters.
First you need to ensure that there is indeed a restrictive covenant on their property, there may be on yours but that does not mean there is on theirs.
If there is, write to them and advice them of the restriction. Should they ignore that, then you would need to attempt official mediation with them to stop and remove the breach.
Finally if they refuse mediation, then at that point you can the. Decide to take the matter further and go to court.