The best thing is a pair of Buffalo mittens, which get wet but stay warm even in gale force winds and snow. Sealskinz mittens if available might be good, I doubt it though.
Ex-army gloves from Afghanistan are the very best gloves money can buy, get a pair slightly too big, they stay warm even when they are so wet you can wring the wayer out of them, which is what I discovered on Saturday morning.
Ebay is the place, about a tenner the price. On the FNRttC trip to John o Groats they were nicknamed The Magic Gloves Of War.
Sealskin socks, neoprene overshoes, but my feet turn to stone and hurt all the time at quite reasonable temperatures.
Also, Rainlegs are very good, about £25 I think, from the Netherlands. A bit like the chaps cowboys wore on their legs in the rainy scenes in films, you don't get the 'boil in the bag' sensation and the rain is kept off the tops of your legs. Also light to carry, and fold up into a clever belt thing that you can keep around your waist and not notice while cycling.