Mark,
You've got an Eriba Familia right? First of all, you shouldn't have too much trouble owning an Eriba, they are not popular with the usual suspects.
In fact we haven't heard of an Eriba being stolen in the UK, but it's not a good idea to tempt people - so:
1. You have an AL-KO 1300 stabiliser coupling, so buy an AL-KO 1300 Safety and Safety ball (may come in the package).
When you stop at a service station, fit the lock and remove it just before you set off. It's not a good idea to have the van locked to the car when you are driving.
When parked, fit the safety ball (stops the thief from using an undersized tow hook) and the safety lock.
2. You have allow wheels with a locking wheel nut? Then buy the EuroClamp Bulldog - this clamps around the kerb side wheel.
The Euroclamp needs regular lubrication of the lock.
This is the basic minimum, and it should be sufficient for your insurance.
Robert