I couldn't find a figure for the max. towload of the petrol Mini, only of the diesel, and that's 650kg. Assuming the same figure applies to the petrol, too, you would be pushed to find any caravan that falls below that figure. Even the smallest Eriba, the Puck, is rated at 700kg. I think you'd have to resign yourself to a folding caravan if you want to tow with a Mini.