Hi Brian LD
There is a good storage site just inland from Mazzeron at isla plana but it is only storage not residential so you would have to take the van off-site to live in it. From memory it isjust over 1 euro/day, but they also do service and clean the van etc. if you wish.
If this is any interest i will try to get better details for you. there are several sites at Mazeron/ Puerto de Mazeron not too far away, but you would have to arrange for the van to be towed there.