Am currently fitting a tow bar to take a bike rack, I have a Mottez 4 bike rack, the advantage of this particular one (and similar from thule) over a rear door mounted and roof mounted ones is more bikes can be carried they are away from the car so don't knock it, they are secured individualy and don't bang into each other, I can get the whole families bikes (4) on one rack, the rack can be tilted to allow access to the boot, you don't need to put your back out raising them to the roof and hoping not to drop them, no increased vehicle height. Disadvantages; cost of tow bar if not fitted, cost of carrier £300 up depending on type and number of bikes, extends length of vehicle. These type of racks seem few and far between in this country but are extremely common on the continent.
jus. :shock: