v. short term highland storage

We love scotland, particularly the Bunree site, but have decided to do something different this year and tour up uist/ lewis. Not being brave/rich enough to take our caravan with us, we'll use either hostels or wild camp while we're there, but would love to spend some time before and after on the mainland in our 'van. I know rules say we can't leave it on site (incl on a CL) unoccupied, so what can we do with it for 5 or 6 nights?  thanks