Flannel-lined denims if you can find them. I’ve got a pair of Oakley ones I got in a sale many years ago, and they’re nice and snuggley when it’s cold. I’ve also got a couple of pairs of Danish Army combat trousers that I bought when they offloaded their entire inventory after changing from a three-colour Flectarn to Multicam like our troops wear. They went from around £75-85/pair to £16, so I got two pairs and a jacket for the price of a single pair of combats – the jackets were around £100 at the time.
What makes them so nice wear is they’re 3/4-lined, and very tight weave cotton, so virtually windproof.
But also too damned hot for 3/4 of the year!
Just checked out Amazon, and they do Key Apparel relaxed fit straight leg 12oz denims with cotton flannel linings for £40, so worth a look, team up with a heavyweight Uniqlo flannel shirt and a nice thick woolly and a windproof top and yer sorted.