If the temperature falls below 7c then winter tyres come into play. Winter tyres contain more natural rubber and silca and don't harden up in the cold like regular tyres which allows them to key into the roads surface.
Vredestein are unheard of by most but they really do make great tyres. They also win awards every year for their winter tyres.
My mother has a 2008 Cooper on 15"'s with the original Michelin's and they seem to grip like hell, although she hasn't let me loose in it yet

First post btw, I only signed up because I noticed the link pointing to my website from this thread.