Perhaps not the right forum for this as more a bushcraft item I guess, but I have a mens size small (fits more like a UK medium) Fjallraven Granit shirt in green, work once on a cold evening in the Lakes in Jan for literally 3-4 hours. Comfortable warm shirt, obviously not as warm for the weight as synthetic or down but should stand the test of time. Probably more suited for a bushcraft weekend with a static camp site and you need something more robust than a lightweight down jacket.

50 incl. UK shipping.