So, the manual says not to use snow chains with 195/55 R15, which I have on my alloys, as they can damage the plastic trim.
I'm trying to decide between risking it, and getting snow socks which are apparently legal in the Alps but a bit rubbish.
Anyone have relevant experience or tips?

no experince but i seen a set of socks sold over here that we kind to alloys and good grip on snow they were made of some strange fabric, i was tempted to get a pair myself.

I use Autosocks on the Mazda RX-8 as it's bloody rubbish in the snow. They're pretty amazing things made from nylon fabric.