no, the fr deisel is 100% legal to tow with. it isn't the chassis that is the problem with the cupra r; it is extra engine strain that they don't want to warranty. I only tow go kart about so not much strain.
there are 2 parts to the detachable towbar. you have to get the fixed towbar for 150 ish, and then the quantum upgrade for a further 100 ish.
the only 2 difficult bits with fitting are cutting the bumper (make sure it is marked up perfectly and you've got a decent hacksaw); and wiring the electrics because not all cars have the same colour wires for each function (with some time and a multimeter this is overcome).
there are 2 parts to the detachable towbar. you have to get the fixed towbar for 150 ish, and then the quantum upgrade for a further 100 ish.
the only 2 difficult bits with fitting are cutting the bumper (make sure it is marked up perfectly and you've got a decent hacksaw); and wiring the electrics because not all cars have the same colour wires for each function (with some time and a multimeter this is overcome).