In reply to Fultonius:
Thanks for the advice.
For anyone that's interested, I tried on a couple of the options discussed above, namely, rab calibre and OR cirque.
They both had a good cut for climbing with a good taper at the ankle using zips or drawcords or both to reduce / increase volume. The Rab cut was slightly better as the OR trousers I could see being slightly too tight around the thighs for some, but good.
The OR trousers had better features overall (i.e. loops for braces, velcro waist adjuster tabs so you don't need a belt, lace hooks, grommets for attaching shock cord round your boots, draw cord and zip cuff, more pockets (though hand pockets are very small)). Rab trousers weren't bad but I don't think they had brace loops, they have no lace hooks and the attachments for shock cord at ankle are just fabric loops though probably fine.
Obviously the Rab trousers have a membrane and the OR trousers don't. I would have thought the Rabs would be tougher but they actually felt pretty soft and, apart from the reinforced bits on the inside leg and knee, you could probably put a few holes in them. The OR trousers feel pretty bomb-proof, very stretchy and I reckon they would take some abuse.
Overall, on initial impressions, the OR Cirque feel like a better option for Scottish winter climbing unless you really want a membrane. They are also cheaper and I don't feel like the Rab Calibre really merit the hefty price tag.
I will probably go for the OR Cirque but I want to try on a pair of Patagonia Alpine Guides first as they seem to be about at tough as you can get, which is mostly what I'm after.
Post edited at 13:54