A friend of mine has a friend who has a friend who lives in southern Portugal. I might be able to park the van there. If that doesn't work: there are guarded parking areas near airports where you can leave your van for several days. I think it's something like 5 Euros a day.

But even if I leave the van somewhere unattended: I take my laptop and wallet with me. Other than that I don't have much valuable things in my van: If someone wants to steal my underwear that I've been wearing for ten years: fine go for it.

At the end everything in my van is replaceable. Including the van itself ;)