The rear bumper is in two halfs, top half is the same on all mk5s and the bottom differs between GTI, R32, normal spec etc. You'll only need to replace the half that's damaged.
I've got a top half if that's the bit you need - it's off a car with parking sensors though. And it's in blue. I'm not keen on posting it, it's exactly the kind of thing a courier would damage. But if you're nearby and interested let me know. I'm in South Yorks/North Notts.