Something to think about before you go ahead, copied from bosal website
Tow bar design
Tow bars are reviewed on an individual basis, and only those that meet the European Courts safety and quality standards are considered type-approved. As of 1998 in the UK, only Whole European Type-Approved Vehicles can be fitted with European Type Approved towbars. To ensure that the tow bar you are purchasing is safe and compliant, always look for the type approval plate.
Manufacturers design towbars using data such as;
The car manufacturer's specified fixing points
Gross Trailer Weight
Gross Vehicle Weight
As this data varies depending on the make, model and year of the car, it is important that you invest in a (type-approved) vehicle-specific tow bar.
I've done it but won't any longer, if it's not type approved it's not legal in my understanding of it. Have an accident whilst towing I think it would be a world of legal pain.
Just my interpretation of it...