In reply to stevev:
Thats not quite strictly true regarding temp range nowadays. For the old standard winter tyres then that was pretty correct but now quite a few manufacturers are marketing all weather/winter tyres and there is no difference. What dictates mileage is the silica content.
I had a set of Michelin Pilot sports fitted to my Audi and the RS4 and they were lethal in anything more than damp. I found out later from the Michelin rep that they were not suitable for all year use!!!!
I think with al the issues of last winter most insurance companies are reasonable providing you tell them and the tyres are correctly speed rated and CE marked.