Tony you daft cunt. Why do you want 215/40/17's?? The 10mm difference in width will make no noticeable difference to the amount of grip, but will just increase the chances of the tyres catching the arches and also will the car more prone to tram-lining and torque-steer.

Go for 16's for the track. That way you can put either a 195 or 205 width tyre on and also have an easier prospect of finding slicks in a sensible size.

Fitting them over your brakes will be the next challenge though.

Mine do I know, but I had to modify my calipers, before I got them repainted and they are still really close to the wheels.