Re: gtv bike rack???
Yep I have a rear bike rack on my GTV, but its not a current Halfords model, it's something I picked up back in '94 from a Makro store of all places. Basically you should be able to find a rear mounting bike rack for hatchbacks (like a mini or similar) and fit that.
It just has to be small enough to fit over the boot lid. You put the top hooks/mounts at the top of the boot lid below the rear glass, and the bottom hooks around the bottom of the boot lid.
You end up with the rack's rear pipes (the bit that carry the bikes) sticking up at a slight diagonal angle, which I find is quite reassuring as it seems less likely the bike will fall off the back! If you're strong enough, you can even lift the boot lid with the bike on top!