In reply to chem_j:
I find that if I wear too much I get clammy and then cold. I also boil when moving, so the walk in it's a synthetic baselayer and a pertex top (and don't wear the latter if there's no wind worth speaking of. It needs to be about -10 to add anything warmer if I'm walking up hill. I only wear waterproofs if it's raining, and take them off the moment it stops.
Gloves - smartwool or polypropylene liners - always - and for the walk in. Then a pair of BD punishers over the top.
Legs - windproof softshell with decathlon winter running tights (not as thick as powerstretch, but same principle)
When I start climbing - a thin fleece tucked into my trousers then a thick, windproof softshell. Fleece headband over my ears - rarely need a hat with a helmet on, but maybe. Merino double length buff, which keeps the crap out and provides the bank robber look if necessary.
As soon as I stop, the layers go on, including a big ME belay jacket.
Inside the top of my sack is a foam sit-mat, attached to a mini-krab and shock cord. I always sit on or lean against that - makes a huge difference. Rucksack off on belays usually to allow full 'shake your tail feather' and arm waving and back slapping on stances. Never underestimate the power of a full Apache war dance on a stance. Gets everything moving, but does startle the natives a bit though.
The secret weapon? - Nestle Condensed milk in a tube. Lives in the napoleon pocket of my jacket and is central heating in a tube. Available in Morrisons. And hot full sugar Vimto or SIS blackcurrant energy wotsit in a flask. If in doubt go for a big flask and drink it - a 1 litre flask will stay hot all day whereas a smaller one will become warm at best.
And Lucho Delitos (from Condor cycles) for general well-being and happiness and energy. A gel or two can work wonders - one taken at the CIC hut is very beneficial.