Clutch and Brake pedal locks are a good one to stop the general chancers, not cheap though, 90-120quid
Like the clutchclaw
https://www.nkgroup.co.uk/product/vw-bay-window-type-2-clutch-claw-car-security-device/
Steering locks are pointless as easily removed/cut unless its the full wheel type.
Fuel shut off solenoid is a good one with a hidden switch.
Wheel clamps only if they cover the whole wheel, them 3 arm ones are pointless and the clothes-peg like ones can be cut off with a cordless angle grinder in 30 seconds
Main threat these days is the low loaders.
Whilst people don't want to spend much on security, if your vans worth 10k plus then I suppose we shouldn't be complaining about something that is 1% of the van price