My wife wants to drive her car year-around, mostly commuting. We get some snow here but not a lot. The typical storm drops 1-3" and the roads she uses are almost all plowed and treated, with lots of traffic. So the snow tires are probably overkill, peace of mind if she really has to get somewhere in crazy weather.
The car has 18" wheels that came with the Sport package. I decided to get a set of winter wheels to take the brunt of salt and sand damage. That allowed me to choose 17" wheels and tires, all the same size. My wheels are 17x7.5J. The specs say they have a 45mm offset, not the 42mm of OEM front wheels. I think that's close enough. The tires are four 225/45R17. They are very close to the OEM tire diameter, close enough that I can't tell the difference in diameter.
I chose Goodyear Ultragrip Ice WRT tires because we had them on our Miata and they worked fine on the same commute. I believe in Europe, the same thing is sold as Dunlop Winter 3D. The speed rating is not too high, so if you want to go faster than 112mph, pick another snow tire.
Changing wheels means getting new tire pressure sensors. The car eventually found the new sensors once I reset the system. You may need new lug bolts. I got those as a shortcut to searching for wheels that fit the OEM bolts. My wheels had smaller holes for the center cap than the OEM wheels, so I just left the free cap on.
I changed the wheels myself with the car's tools to get some experience in case I ever have to use them. (I figure I'll be too impatient to wait for roadside assistance.) I would add two items to the car's kit. One is a 17mm deep socket. This is because the wheel's bolt holes are too deep and small to finger-tighten the bolts. A cheap one is fine since you are only using it to hand-tighten. Also get some hand wipes or gloves, so you can get back in the car without leaving brake-dust handprints on everything.
Here is a before and after photo. The looks could be better but I think it's close enough for winter driving.