I've used a Blizzard jacket a number of times over the last few years and it is surprisingly warm for its weight. It's hardly fashionable and amongst my friends is referred to as the baked potato jacket . Now that they are available with sleeves it is completely waterproof. Can it be carried instead of a conventional waterproof during fell races, as I often prefer to run in a windproof?
At 250g and about as warm as a lightweigh duvet jacket the Blizzard jackets make excellent emergency garments. They will fit in a standard bum bag.
Available from lots of reputable UK shops!