Insulated over trousers come into their own in dry climates at high altitude, where the temperatures plummet as the sun sinks and you're often setting off on pre-sun cold mornings. For that, I recommend not full length (the bottoms can get wet) and full length zips so they're easy to remove (their big advantage over long johns). Mountain Equipment 3/4 Compressor Pant are good for synthetic ones though Bozena's are Primaloft, not Polarloft, and the Women's version is no longer on their website. I have a pair of Pajak Ghost Shorts - they actually come to below the knee and add a surprising amount of warmth. They're the only non-full-length down trousers with full zips I know of. Their only downside is the zips are one-way and open from the bottom up so access to the pockets on the trousers underneath is not as easy as it could be. For the UK with its rain and its cloud cover lessening the day/night temperature variation, I imagine they'd be useful less often.