After 4 years of ownership in various guises my conclusion is that unless you are doing multiple trackdays and car is not a daily drive STICK TO OEM SUSPENSION.
It is far better suited to UK roads than any aftermarket suspension I have seen. Coilovers at thecrear ovviously have serious warranty issues and potential for refusal of goodwill on subframe cracking and will make the road ride slower and harsher.
I guess thus advice wil fall on deaf ears. I certainly ignored it 2 years ago.
If you do ignore it, try Intrax IK2