In the U.K., Cotswold (www.cotswold-outdoor.com) carries the Macpac Mountain Pants. These are a bib-style, all-around outdoor overpant that would work well for all the activities you mention. They're made from Gore XCR, the newest iteration of that long-popular outdoor fabric. Cost is high but not too outrageous200 pounds Sterling. That's about US$350, which is par for the course. A comparable bib in the U.S. would be something like Marmot's Pinnacle Ice Bib (www.marmot.com), which is US$350.
You can always shop for sales and specials, and I'm pretty sure you'll find a better price. In the U.S., for instance, Sierra Trading Post (www.sierratradingpost.com) has The North Face's Nuptse Gore-Tex bibs on sale for $230, down from a regular price of $335. If you can fit into a small or medium, Sierra also has Mammut's exceedingly nice Eiger Pants, which like the Nuptse bibs use Gore XCR, for a mere US$166down from $395. Now that's a helluva deal.