The greater the number of security measures that are visable then the lower the risk of having your van nicked.
Silly things like parking the van front on to the drive, parking your car tight to the side with the wheel clamps on, having a flood light on a pIR etc all distract MR Thief.
You'll never stop a professional, but if you make life to time consuming and noisy to stael your van, he'll ****** off to easier pickings.
Just think of it like this an hour spent un-locking the van means half an hour of risk to a thief and that is a good 20 mins too long as he want's to be gone well inside 10 mins. That's why they carry oxy acetylene cutting gear and use drop boxes. Seconds of delay to them is like hours.
Another little tip is to use anti vandal paint (non drying type) on the wheel clamps and padlocks. Sure, you'll need to use gloves to handle them and carry a spare dry clamp for use on holiday, but just think how many potential finger prints can be left behind, or a trail to follow.
I have a can of luminous paint strapped under my van with a bung in a small hole in the can, which is connected by fine fishing line to the ground. When thiefy tows the van off a litre of paint drips for a good twenty miles and being luminous is dead easy to follow at night.
All you have to do is think like a thief and you'll foil a thief!!
Steve L.