Both are good points of course. I had spoken to my own insurer (Aviva) who said as long as all 4 tyres were the same, it was fine (rightly they didn't want summer and winter/AS mixed) and did not affect the insurance in any way. The 3PSF symbol means they are treated as winter tyres for these purpos...

I've recently had all-season Vredestein Quatrac Pro fitted, they have the Alpine mark, are the right size & speed rating (W) and exceed the load rating but are not N0 marked. Vredestein are a long standing Dutch manufacturer, known for their A/S and Winter tyres, not well known in the UK though....