Hello Martin,
For many caravan owners the choice of storage is limited by the fact that their insurance insist that certain security measures are used, and many include the use of a CaSOA affiliated storage site.
If you ignore your insurance companies small print instructions, your caravan is not covered, so to use a site such as the one you describe may not only increase the risk of left or loss, but it may also absolve your insurance company of liability to pay up if you do suffer an incident.
The choice is yours - but check your insurance details