In reply to andrewmcleod:
Charmoz's are great. Super light but you might get cold in deep winter unless you size it for a very warm sock. Even lighter would be the Scarpa Rebel range, which I can only assume is the reason Ueli Steck is so fast.
If you plan on doing more snow/alpine based routes (as it sounds) then check the Phantom Guides, if you have cold feet or are just ambitious in the altitude department then you could up it to the Phantom 6000'S (though overkill for UK really).
Other super warm/durable boots could be La Sportiva Baruntse's (if you can find them around, some shops in mountain country have them). Or even something from the North Face Verto range, depends on what fits you!
Us vegans are spoilt for choice these days!