As above, tights under shorts? trousers? leggings? What's good. Always just wore shorts but fancy being a bit warmer this winter.
Endura stealth leggings they are the monkeys knuckles for any bad, wet, cold and wintery weather!
get something made of goretex or equivalent - I have some of the Endura 3/4 shorts just keeping the wind out makes your legs warm and the waterproof material stopping you getting a wet bum is great.
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Over the knee roubaix bibs. My most worn cold weather cycling clothing over the last 5 years. Great on their own if you want, work under shorts and not quite full leg cover.
The Gore Oxygen biblongs are superb.
I got the ones without a pad so I could wear them on consecutive days without having to wash 'em all the time.
I just stick some liners underneath.
Very comfy, very toasty but perhaps a bit warm if you ride hot.
They've lasted four winters and still going strong.
Roubaix knee warmers are brilliant, fine down to some pretty cold temps, really good for changeable days, easy to put on/off mid ride unlike tights/bibs.