My caravan is "on it's way" - and don't currently have any plans to sell it - but eventually I may. My understanding is that as long as you have complied with Australian Regulation's - then the caravan can be sold. Maybe speak to another dealer? Also look at the Private Market - you may get better returns.
The trader you contacted may not want to have an European model on his books…I drove past a few dealers in the Sunshine Coast yesterday but didn't see any European models there - but that doesn't mean they won't trade…if they can make money on it - they will buy it...