Ordered a Pirelli at the beginning of May.
10% discount can be had (or thereabouts). You've just got to find the dealer willing to do the deal. My Pirelli was already on order by the dealer so expecting it June/July.
See my bargaining skills here!
http://www.golfgtiforum.co.uk/index.php?topic=87063.20Personally, I would have just gone for another GTI had they not been prepared to discount the Pirelli but, it does have the following extras on it which have got to be worth something over the standard GTI (and I couldnt resist an extra 30bhp!)
You also get the following as standard over GTI
18" Pirellii Alloys (cost £465 on GTI)
Metallic/Pearl Paint as standard (£365)
Body Coloured Spoilers Front Rear and Side (£?)
Darkened Rear Light Clusters (£?)
Heated Front Sports Seats with height and lumbar adjustment (£?)
Tinted Rear Windows (£?)
Front Centre Arm Rest (£120)
I went for the Reflex Silver as I didnt really like the other colours. I suppose as the run out continues they will probably release more colours including the Sunflower yellow - thats my guess anyways!