I've found an m-sport bumper in my colour and it seems easy and cheap enough to source grills, adaptors and fogs so i think that's my route.
I really like the aero but can't find it anywhere, plus i'm not sure how good a job i get repairing the existing bumper anyway.
As far as the z4 goes, she's sitting in my garage tempting me to take her out so i'm burying my head in mods for the e91 to attempt to ignore it. Think i'm going to have to put her up on eBay as i've had no interest in it at all so far. shame, she's so pretty!
thanks again lads, will keep folks updated.