what do i use to protect the body work of my hobby caravan?

Acrylic or Alluminium body
I would give it a good clean with quality car shampoo not household liquid soap that has salt in it.
Then polish it with again a good quality long lasting car polish, that should do it. Or if dubious contact manufacturer or local caravan accessory shop and they will surely tell you and may have something which will last through storage time although car polish has a long lasting time factor before re-coat.

bob
May 2009