If you're serious about winter riding, especially more than just a short run out then i'd strongly reccommend a heated waistcoat to fit under your leathers. By keeping your central core warm, you keep warmer blood pumping to the extremities.
Also Hein gerickes Pathan gloves £30, the ones that make you look like a 2 fingered crab type mutant also work very well. Daytona waterproof boots, a size larger than nornal so you can get a couple of pairs of thick fleecy socks work for me.
You'll end up waddling like a duck and its murder going for a pee.
I crossed the Pyrennes in a blizzard in March when all the locals were fitting snow chains and stayed nice and warm. Doesn't stop you falling off in the snow though!
Also find a car works very well when the weathers bad
