I run winters as well, on steel rims (will put them on this weekend). In the long run they don't cost any more as you're saving your summers. Never mind the snow, they make a big difference on cold wet roads. I can outmanoeuvre BMWs in my Jazz. Hilarious to do. I reckon twice the grip of the Bridgestones at 2C say. You can just lay round the roundabouts like a hooligan, its almost disconcerting.
I got them last year as in the ice/snow I had to resort to the Volvo to get to work. The Jazz wouldn't even go on the level. No doubt a better set of summers would have helped, but I went the whole hog. £300 quid for 4 tyres on steels from Mytyres.com. Dropped to a higher profile on 14" rims, narrower as well, helps shift water on the M9 which suffers from standing water.
Recommended.