[Noggie]

I have to agree with Ovesund here.

I live on the west coast of Norway, so we have a very similar winter climate to Scotland.
I got my i3s in November last year so my experience is more or less only from winter use.
If you go full electric, make sure you get the -19 model or newer with 280-310km range (120ah). Will save you range anxiety, especially in the winter.

My experience from this winter.
-Use preheating if possible, will extend range and doesn't use too much power, not to mention how nice it is to get into a warm car. (if charger plugged in it won't drain the battery).
-I have a heated garage, I typically keep it around 12-14c all winter. Hence I have typically seen rage around 250km on a full charge this winter.
-I did a longer trip when it was -14 outside, (car was warm and preheated when starting) after 110km with a nice warm car (23c), my charge was at 54%, so at those temperatures you will probably have 220-230km range. More if turn the heating off, many with the gen 1 (60ah) and 2 (94ah) i3's over here run "cold" cars and drive with thick coats, cloves and hats to get more range, the 120ah will allow more comfort in that respect.

All in all, my i3s (120ah) had no issues this winter what so ever. Traction Control is great in this car, I have the Nokian tires as well and had no issues what so ever.
I actually went as far as to say that this car was "boring" as no matter what I did I could not get the rear to step out, other than switching TC off, something you can only do in the "s" model.

I would recommend getting a type 2 charger at home if you can.
I have an 11Kw charger, and it will charge my car from empty in about 3 hours at home, even a 30-40 minute charge will get you the range you need for most things with one of those.
As you are in the UK, you can get the same Easee charger I have, which is great.

I typically charge my car 1-2 times a week, depending on use, my office commute round trip is is 40km and a full charge got me to work 5 days and som local shopping without any problems this winter.
I just passed 3100km, and I have put 706kw of power in it according to my charger, the App say I have used an average of 17,2kw/100km this winter.