Hehe, yeah the towbar is a nasty little bugger... it looks small but it's not.
Behind the bumper there is asteel bar that runs across to each side and is welded to the towbar. If you take the side panels off inside the boot you'll be able to see the bolts holding it on.
Then underneith the tyre well from memory there was another 2 bolts.
Then near the very back just above the tow bar, I think there was another 2 bolts. You also have to undo everything holding the bumper on.
It's a very frustrating job, and we managed to rip the bumper from the fibre glass support so it's probably best you take it to a mechanic and save yourself ripping your hair out(and let them rip their hair out instead. lol)