Glenn, your household insurance will NOT cover caravan items unless they are actually IN the house, as in storage.
The CC insurance has provision for those items in its quotation, you specify what you want covered, they cover it.
Similarly, if you take house items away in the van, such as Sky box, you should have this listed for an extension of cover for items away from home, or if you have it stolen, they will not pay out.
As with all insurances, make absolutely certain you have the correct cover for what you intend to insure, or the getout clauses will defeat any claim you may make.