Without checking online to see if anything has changed since I bought my most recent pair...
Ron Hill Bikesters are the way to go; there are different versions, so you don't
have to sweat your b*ll*cks off in decent weather.
I have a heavy duty pair that have a waterproof treatment that is reactivated by tumbledrying after washing. I then have a lighter pair that are intended for general all-round wear. I also wear mine over padded 8-panel cycling shorts (they are more comfortable because 5-panel shorts have to stretch in more directions to fit) with chamois inserts, though some people prefer synthetic. I prefer the chamois and wash them religiously after every ride...
...the secret to any weather riding is LAYERS; several thin layers will keep you warmer in colder weather, and are easier to 'fine tune' as things warm up. You should always carry a small pack of some sort anyway so you will have room to stow stuff as you see fit. Always buy the best you can afford too; decent stuff wicks sweat away from the skin to the surface of the garment where it quickly dries so you aren't even aware that you are 'perspiring.'
Trendy, loose clothing is naff because once you get wet you really feel it; the right 'tight-fitting' stuff is supremely comfortable because it moves with
your skin rather that chafing over it. I have ridden countless miles literally soaked to the skin in bib-shorts and short-sleeved top with absolutely no discomfort whatsoever - well, not in winter obviously!
It is quite surreal to strip off after a wet ride and find that under your waterproof Bikesters your legs are bone dry!
If you buy the right gear you will never feel uncomfortable whatever the weather