Have you thought about getting a towbar fitted and using a towbar-mounted rack? I've used one for the last 3 years and found it way, way better than the other sorts of racks in lots of ways. For starters, any rack hanging off the bodywork of the car is going to rub at your paint, and eventually scratch or chip it. If a strap gives way, or you hit a speed hump, the bikes could shift, causing a pedal or similar to take a chunk out of your bootlid (this happened to me, I was furious). Then, most rear-mounted racks let the bikes rub or knock against each other, damaging the paint or components on the bikes. Most of them obscure the rear lights and reg plate, meaning you will need a light board anyway. They'll probably also hold the bikes at such a height your rearward visibility will be next to nothing too (though if it's anything like my 147 the rear visibility sucks anyway!).
As you probably guessed, I won't go back to any other sort of rack now. It does work out pricey buying the rack and getting the towbar fitted, but then that's it until you change your car. The racks will fit just about any car with a towbar. And it's always handy to have a towbar (for punching a hole in the radiator of anyone cheeky enough to drive into the back of you, for example. Oh, and for towing stuff
). I've tried all the other types of bike rack over the years and found the wheel support towbar ones the best, by miles.
Please feel free to ignore all this though, I won't take it personally