Very nice Sam!
Did seeing mine tempt you more then?
From what you've said, Id go for Darklines, 313's (standard silver colour) and a light tint all round.
The reason I say that is because of the car colour, dark rear tints would make it look a bit like a van. (Ive got a pet hate for that look!)
Performance diffuser is a good idea, and one I'm thinking about, or I might go for the 335 look.
The only thing I'd do is lower it and maybe LCI roof rails (another thing on my might do list!)