I'm not sure sure all-year tyres are ok even a 4x4 during the winter. Even if the authorities deal with snow well during the winter, there's still slush/black ice etc. The other half skidded out on a roundabout last year in our X3 and hit another car (parked on the outside). She wasn't going fast but it was ~6am in the morning and she was likely the first on the roads. Mind you, London's been pretty unprepared for any kind of real 'winter' weather so I'm planning on getting winter tyre sets for both of our cars.