If you use 'cold weather tyres' in winter, then there aren't any concerns. And this winter I've been on 205/60 R16s on an F30 320dED with no problems even down to minus 7C. There is no car better than the F30 320dED, so I cannot recommend anything better. But you won't get one for £15k, so probably a good idea to think along the lines of a Mazda 5 1.6D TS2 (or a 2.0i TS2 if you prefer petrol). This comes on 205/55 R16 Toyo J48 tyres which are excellent and you simply will not believe the outstanding combination of ride comfort, suspension compliance and grip, especially when you hit a bump or rut on a corner.