I looked at getting some winter tyres for my 18's. Having seen the price for winter run flats at that size, I picked myself up off the floor and bought the 17' seteel package from BMW. . .doesn't look bad at all!
Only issue now is that if I have a puncture I have no spare. . .looking at options.
BTW Mario - Did I see you near Irvine on Saturday? Silver X1 with winters on passed me. (I was in an old green Merc W124)