Back here I mentioned the diffuser I recently bought; laser-cut, great quality & price 
http://www.exiges.com/ubbz/ubbthreads.php?ubb=showflat&Number=141888&page=4
Just had an email from the guy who makes them which I thought might be useful for anyone here who’s looking for a diffuser as he will have S2 as well as S1 versions soon.
The one I bought is listed as an ‘extended’ for the Elise but is 140mm longer than standard and just comes level with the rear of the Exige clam.
He sells through eBay: bb26racinguk
(Mod: Hope I’ve not broken any rules here )