George, I've just responded to you on eBay and inadvertently answered this question.
If you have a GT-S (4.7), the bootlid has like a ducktail flip to it (integrated spoiler) and the MC spoiler will 100% not fit that. If it's a 4.2 with a flat bootlid, the spoiler will fit that. It's bloody crazy that you can't fit the spoiler to the 4.7 'S' without buying and spraying a new bootlid! Aarrghhhh!
Anyway, this kit for £1k....does it include front splitters and sideskirts and is there more than one available?? It's worth £1k just for the front splitters as, per my previous post, Maserati want over £2k for them alone - even on Formula Dynamic's site in the US, the front splitters are $1,500 PER SIDE and they normally are a lot cheaper than UK main dealers even after shipping (I know this as I'm currently looking into purchasing the carbon steering wheel from them which is half the price of what Graypaul want from me...I'm only holding back as I need a new airbag too as my current wheel is red. Double aarrgghhh!)