We do a lot of winter hill walking in all weathers and one of the best bit of kit I've got is a Rab long sleeve base layer.
http://www.cotswoldoutdoor.com/rab-mens-meco-250-long-sleeve-zip-tee-19110447?id_colour=107
Yep bit expensive but your getting top kit and amazing warmth next to your skin. team it with a fleece, and smock and you'll be warm, dry and still not look like a Michelin man!!
Other base layers are good and make a massive difference to keeping you warm instead of sweaty damp holding cotton tee shirts.
Nikwax wash is superb for waterproofing your kit BUT follow the instructions.
I'm a pretty crap fisherman ( just starting out) but never cold!!!