My 718S is my daily driver. It's equipped with black 20" Carrera S wheels and Pirelli P-Zero summer tyres. When the temps approach freezing point the rubber really stiffens up and has very poor traction if the road surface is wet, icy or snowy. Last winter I had to avoid taking it out on days when there was snow or cold/wet conditions.
This year, at the start of the winter season, I bought a set of barely used 981 Cayman/Boxster 18" OEM wheels (part number 981.362.120) on ebay with 235/45 R18 (front) and 265/45 R18 (rear) Dunlop SP Winter Sport 3D tyres. There was 6mm of tread left all round. The wheels were in excellent shape.
I had the wheels powder coated in gloss black. Going black was to match the colour scheme of the car and I think smaller wheel size is far less noticeable when it is black and blends with the tyre. Only unexpected issue was when the rear tyres were remounted, the sidewalls blistered - probably due to the age of tyres and wider rear wheels. To replace them, I bought a pair of brand new Hankook Winter i*Cept Evo3 W330 265/45 R18. I opted not to replace the incompatible TPMS on the 4 wheels and put up with the dashboard idiot light instead (due to the cost and the hassle of taking the tyres off and refitting them).
The total cost was £1,140 (£600 for the wheel set, £320 for the new rear tyres and £220 for powder-coating and fitting).
I am very happy with the results. It grips like crazy in freezing and snowy conditions that we have had over the last week in the UK, the black 18" wheels don't look out of place and there is the added bonus of a comfier ride during the winter months. I plan to switch back to the summer set during the first warm weekend in April.