In reply to Father Noel Furlong:
3 words - Alpine Guide Pants.
Look no further.
Patagonia gear is 'reassuringly expensive', perhaps, but 100% Bomb Proof. Plus there's a lot to be said for getting what you pay for. -15C and 20mph winds on the glacier runs? Not an issue, toasty, and none of the walking in bin liners feel of over-trousers when down low either.
I tend to wear normal Guides in the UK and Aplines in the, er, Alps. The only issue I have with the Alpines is that it's a teensy bit of a struggle to get them down over my favourite decidely old-school ski boots. Newer hired boots, no probs.