[Crazy Dazz]

WTF?
You don't own a caravan?
And so because you don't have a caravan, you feel the urge to tow something else?

Are you trying to test your car's performance as a tow-car? Is that it?
So you want something to approximate a Caravan?

IMHO, the biggest issues in towing a van are:
1) Braking. Unfortunately you can't really trial this, because most hire trailers will have illegal and usually non-functional over-riders.
2) Weight Distribution. By law you're only supposed to have 10% of te weight on the hitch, but if you have to choose, more is better than less. Vans can be rebalance by moving water tanks, gas bottles, and spare tyres. It can be hard to re-balance a car on a trailer, as you only have tow choices.
3) Side Winds, including those caused by passing trucks. A large covered furniture trailer would give you your best approximation of this, but they're smaller than most vans.
4) Drag. Most people think in terms of power to weight, but at highway speeds its the drag that kills you. Again, a tall covered trailer would be the best approximation.