Towing with a car can slip through vosa. Vans can't.
I have a touran to tow with. The listed tow capacity is 1500kg. But there is now maximum tow weight for cars , just the 80% weight guideline.
Vosa are mainly doing people under the customs regulations, but not 100%. It is far harder for them to get average joe towing with a car. It's down to a police prosecution for that.
It's a very grey area that people have different story's about.

Also spotted the trailer for sale and as I said its not much more to buy a new one.