Winter wheel/tyre setup

Hi all,



I've got a BMW 318 Sport with MV1 style alloy wheels, I'm not sure of the size of the tyres, all I know is that they are a staggered fitment with wider rears.



Living in the UK we aren't certain to get snow each year, but I would like to get something in place ready if we do.



What is the best idea, should I just get two rear MV1s and get some snow tyres fitted, or is it better to get narrower wheels all round?



Also which tyres are recommended for use in snow, I saw the Michelin Alpines get good reviews but they aren't cheap!



Any advice would be appreciated.



Thanks