Whilst at the CAT driver training event I discovered that the Rears, fitted by my friendly fitter were pattern EX. Everyone else on Bridgestones seems to have KXs!
Checked with Bridgestone and they confirmed I should really have got KXs for the Z, but that if I hadn't noticed any problems in the 5000 miles on them they would probably be ok! All that after 135mph on the banked circuit!
Lesson: Get a knowledgable fitter/specialist!
Someone asked for the details of the place I finally ened up at....
The aligment equipment is made by Hunter Engineering (USA) and your local equipment can be located by going to www.alignmycar.co.uk.
The fitters I used were at Purley on the outskirts of Reading, and they are part of the merityre group, details www.merityre.co.uk
Cheers all!