Rich, if you're going to do it then you'll need to go OTT on the whole car to make it work IMHO. I'm talking big bodykit, big spoiler, big wheels, the works basically. I got away with mine as it's only ever a temp job for LM this year, wouldn't dream of keeping it on semi-permanently. You'll also need a big budget for it if you want to do it properly GT-style, bear in mind I spent £150 on cheap stickers and fitted 90% of them myself: You could easily spend anywhere up to £700 on vinyl and I'd get the experts to put it on as small stuff is a piece of cake, but you want the big stuff to look right. By that time you're getting to the point where a decent paint job is almost looking like the cheap option...!
Have a word with the guys at Raccoon up in Woolpit, they can do the whole design for you to your specs and will use their quality vinyl. No harm in asking, anyway.