A lot depends on where and when. Country walking in winter does not need a lot of extra layers or you will overheat. I go for slightly thicker trousers and perhaps a fleece with a jacket over, or a sweater with a thicker jacket. Fell or moorland walking requires more specialist layering. I prefer a base layer, fleece jumper, maybe a fleece as well, a good jacket and lined trousers. Don’t forget your head and hands. Cold hands are a misery.