I'm moving to the Scottish Highlands and am considering whether to buy good all-seasons tyres or winter tyres and a set of spare wheels.  Does the panel recommend 16" or 17" rims?  And what tyre width would give the best snow grip?

Size is of some importance, it depends of your preferences, road conditions and what type of winter conditions you will struggle with. 16" has more rubber height, will be slightly more comfortable and may handle rough, bumpy conditions better than 17", which on the other hand may be more stable and sporty responsive. But this is marginally. Tread pattern and rubber softness will be far more important for grip.

In earlier days, it was claimed that a narrow tyre will have better grip in snow. But today it is said that width is of lesser importance. I am not sure, I use 205 wide winter tyres on my Octavia and are happy with that.

I would definitely go 16'' - many of our roads up here are in a deplorable state,it has gone waaay past potholes on some roads and you end up trying to miss the road damage by 'slaloming' when possible.It is so bad up here now that we do not drive in the dark unless we really have to.

Gawd yes, even A roads have potholes with their own caving clubs.