It's all in a single word: cashmere. I would take three cashmere tops of varying gauge - one fine (good for evening wear), one heavy-ply - great for snuggling up by the fire with a glass of Gluhwein, and one cardigan/wrap/jacket. The great news is that budget stores are huge on cashmere now. If budget is an issue, go to Tesco or George at Asda and get your cashmere for £25 or thereabouts.

The other great addition would be silk camisoles - which are surprisingly warm and great under those cashmere layers. I like moleskin or cord trousers (good at Gap) for apres-ski. They're a bit more laid-back than jeans.