Thanks Jim - I don't get the variant option that you refer to and can't find any new GTIs. I'm looking at autotrader.co.uk so I assume that is the latest version.
For me, PP = increased purchase/fuel/insurance costs and more noise. Haven't ruled it out completely but would prefer the standard model.
I've had both versions of the 7.5 I would say the following:
Purchase price - very little if you look at pre reg/2k miles one.
Fuel - no noticeable different - probably better for the Performance version on a run as its got the 7 speed
Insurance - would guess difference will be almost nothing
More noise - not really, but louder on start up but I actually found my new one smoother and nicer to drive and the gearbox is loads more refined.
But with the Performance model you have better brakes, far superior traction from the diff and a touch more power. I'd say it's a no brainer to go for it.