In a recent Auto Bild winter tyre test, Dunlop SP Wintersport 4d came first, Goodyear Ultra Grip Performance 2 came second and Pirelli Sottozero Series 2 came third. In the Auto Express Winter Tyre Test ,Continental WinterContact TS 830P came first, Goodyear Ultra Grip Performance 2 came second and Dunlop SP Wintersport 4d came third. But UK stocks of many winter tyres were exhausted by last November, so you may have to take what you can get. I think it's best to fit them to a separate set of steel wheels because it is then easier to swap them over. I think the BMW deal is £700 for a set of winters on steel wheels with wheeltrims. That's a good deal. 16s will work better than 17s in winter.