I'm not convinced with a medium sized car that all seasons tyres are the way to go for someone living that far North in UK.
My B8 S4 came with 19" 8.5 ET alloys and I keep them for summer use only, the change date for me is end of October ie half the year to cover the wet Autumn and wet post Winter periods, and for that purpose I bought second hand 18" 8.0 ET Audi alloys as mentioned in an earlier posting.
My logic is, I am keeping my car long enough to use up both sets of tyres and so my summer wheels never get contacted by road salt/grit.
I would think if you said that your car had 18" alloys, my case for suggesting the above would have been weakened a bit!
It really depends on what you are trying to achieve, if you are preparing for being mobile as often as possible, barring road closures, then I'd certainly think seriously about getting a used set of 18" alloys and fitting them with winter tyres also, don't be concerned about keeping them on in North UK until the end of April as they can handle any surprise "high" temperatures that you might experience.
I tend to use Michelin Alpin or in the case of my S4 Pilot Alpin and I've never, so far, felt that they were unfit for that task, though, being someone that has made the choice to fit and use winter tyres in colder weather, I probably do let the conditions dictate when/where and how I drive.