Very rare for me to wear overtrousers, and then normally I wear plastic trousers against the cold rather than the rain; of course, I routinely cycle in long trousers: I don't even own a pair of cycling shorts. Usually I find that for progressively colder weather normal cotton, thermal weave, and then angora long johns not only do the job well but are much more comfortable to wear because they breathe well. I have a Berghaus Goretex jacket but it isn't much chop for cycling, too bulky and stiff and awkward (it's the same jacket Chris Bonington wore up Mount Everest, so it's good on the mountains, which is what I bought it for). I prefer the thin standard type of year round cycling jacket (mine is currently an Altura Night Vision Evo) fitted loosely enough to wear two or three progressively thicker layers underneath but generally I wear only a long-sleeved cotton undershirt and a cotton poloneck shirt under it and depend on the exercise to keep me warm.
You won't believe this but I have -- wait for it! -- a lightly padded leather bomber jacket that is kept specifically for wearing close to 0ēC. It does a wonderful job keeping the wind from interfering with my ride, so that I don't have to slow down, and if the ride is 40-90 minutes (and my rides are rarely longer, even in summer; in winter that's usually all the riding time there is) you don't work up enough heat for it to become hot and sweaty. It's just a matter of judging the point at which it is smart to switch over from a cycling jacket with layers underneath to leather.
Of course, if I were on the bike all day, I'd have to make different arrangements. But these work very well for a recreational/utility cyclist. I've noticed that the people who ride with me started out with the "proper" gear and gradually came to wear everyday street clothes too on their bikes. That raises the likelihood that they felt social pressure to "do the right" thing by wearing Lycra on their bikes, until they saw that I cycle in khakis or cords.
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Remarks about saddles by Martin yesterday make me wonder about something. A bicycle saddle isn't just about the width and the materials; there is a time element: for instance, Gazelle's top-range saddle, a gel job from Selle Italia, is actually rather good to sit on for an hour or two or three, but then becomes sweaty and slippery and hard in all the wrong places; Utopia's base saddle, a Terry concoction with a slit, is a pain in the posterior for the first three hours and then is rather good; a Brooks saddle, if chosen correctly for width according to back angle on the bike, is a pain for a few hundred kilometres and then permanently either the best, or the most hateful, of saddles, according to individual experience.
I sit on a Herman Miller Mirra chair and it has been very successful for me for many years now. The seat is some kind of mesh, and the back a perforated plastic. Though I it in the chair well north of 12 hours every day, sometime 16 hours, both surfaces are, by a combination of inherent qualities of the materials, and their shaping, and their suspension, pretty stressfree on respectively the Jute bum and the small of the Jute back. It's a chair that just works; it's fit for purpose. I'm just wondering why no one has tried turning one or the other of these surfaces into a bicycle seat. What works on an office chair...
