Quad lights are even worse than the bumper!
I don't hate the rear bumper btw, in fact on the red one it looks great, but the XKR needs a cohesive package front to rear IMHO not just something slapped on the backend. It's going to look unbalanced, and if I'm being brutally honest (which I will be because you're a good mate) then it seems utterly crazy to spend more money on making it look pretty when you've still got structural issues to deal with.
Spend the cash getting rid of ALL the rust everywhere, then make sure that all the oily bits are in top notch order, and then go and make it look pretty. No point having a nice arse if you've still got some rust underneath another part of the body.
Quad lights are utterly chav power though, regardless.