found a VW towbar
http://www.volkswagen-accessories.ie/towbar_detachable2
The factory (dealer fit) towbar is made by Westfalia of Germany. Its a detachable, lockable system, and there is a place in the foam that surrounds the spare wheel for it already (well there was on my 05 GTI). Fitting it takes about 1.5 hours, and you need to buy a new bumper spoiler, with the detachable flap from VW (less than £50). The electrics are another issue, you either go for the universal kit, very easy to install, or as I did, the factory fit wiring loom, with all the standard VW connectors, and allows it to work with the check control system and things like non operation of car foglight when towing item fitted ie trailer or bike carrier. It's a pain to install this kit as you have to get the loom all the way through the car to connect both power and to the brake padal connector, but is well worth it over the universal kit. Install of the towbar and new bumper spoiler, is a no cut operation, so no damage to car, and at the time of fitting (2006) was approx £500 cheaper than the dealer fit, for the same piece of kit.
I have always used a Thule towball bike carrier, solid piece of kit.