Thanks one and all. I figured it was probably around drying out and water retention. I looked at some of the suggestions and I have to say so far I do like the look of the Mountain Warehouse ones, though it's hard to see how the Decathlon ones can be beaten on price.
Maybe investing in some thermals or long johns to keep me warm in winter as well would be a good route to go. though the notion of Long Johns does make me feel I should live on sour dough bread and beans and learn to play the banjo ( I do love a stereotype )