Thanks guys, I would like to put in a front strut soon to improve body torsion in cornering, and may chip it. (waiting for a price for a chip) The run flat tyres on this respond far better than the ones I had on the 330i I had before. Even with the lowered suspension on the sports package on the 335 the ride is far smoother and less ridgid than the 330 without a lowered suspension or sports package. I have also found that with the combination of the tyres and suspension the 335i seems less likely to follow the ruts on tar roads. The handling in general is far better than the 330. I am not sure if the technology has improved with the run flat tyres, or because they are now mostly imported from the EU.
As the car does not come with a spare tyre I am a bit wary in changing to normal tyres, cos if you have a problem, your stuffed. The 335 also has a smaller cubby below the flap in the boot and carrying a spare, even a marie is a problem.