ok this might be a completely stupid idea, so I am prepared to be knocked down straight away!
If we took bedding etc in vacuum bags, and took a fully charged hand held vacuum (or a car vacuum? - we haven't got one, so would have to get a cheap one) so that we could compress them when packing up at the end of the trip - would that work? Am I being daft?
(Dh thinks I am, but I am determined that this will be The Best Idea Ever)