18x8.5 ET45 will be perfect on your car. It will give you perfectly flush fitment essentially. I am running Rotiform wheels in an 18x8.5 ET45 spec on my GTD and they fit really nice. I am running 225/40-18 Michelin Pilot Sport 4 tyres too which give a very slight stretch on the 8.5 and a little more clearance. I've done the fender/liner screw mod too just in case. Good luck with the new car 
Cheers dude, same tyres as I've ordered too.
Ordered a few other things too, front splitter from Germany, GENUINE Akrapovic carbon Fibre exhaust tips from Germany not the knockoffs, new red GTD badging for the wings and front.
Also pre-ordered a cool personal plate for it too.
I'll uploads pics of the bits as they arrive
