Simple security steps needed here.
Fact is you simply cannot stop your van from being stolen, but you can make it hard to steal and if it’s hard enough and risky enough they will look elsewhere.
The longer it takes them the more they are at risk, the more they can be seen the more they are at risk.
The more noise they have to make the more they are likely to be heard and again at risk.
You have reason to believe you may be targeted so block the van in with a car or two, park it to protect the habitation door, move the keys ideally to another address and inform the Police of your concerns, check if neighbours have cctv camera, ring doorbells etc and ask them to look for the car.
It’s highly unlikely that these people will be back to nick the van, but you need to have piece of mind so play safe.