writing from Sweden.... not many of us use our minis in the winter, though some do.
You will find the price of a mini on Norway and Sweden to be pretty high, almost a 30 - 40 % more than in the UK. So we tend to look after them and use them only in the summer months. The salt does take its toll on them. I used mine one winter which was real harsh and I needed new door skins, and some general cleaning up and a partial respray (though i wanted to keep the car looking tip top).
Winter tyres - you wont find studded tyres easily. you may find an old 10" set of studded tyres, but they will be old! you will find a couple of brands at 12" and none at 13".
The biggest hurdle will be ground clearance, the channel of ice left in the middle of each lane by normal cars, caused havoc form us. we constantly bottomed out on it.
Though the car drives and handles well in the snow and ice on a good set of tyres.
Personally I wouldnt use the mini again in the winter.