Personally I run snow tyres on the van in winter. If you're going to do something like that then half measures are not worth it really. You have the standard tyres for summer use so I'd get some snow tyres for winter and use them. Just for info, I found that the snow tyres were also much better in the wet aswell with less aquaplaning and better water clearing.
Toyo Snowprox is what I had fitted last year and they were great.
As for the Altea, well I just run ordinary tyres on that and the wife is told not to go out if there's snow about. But the van is out every day working so that needs more.