I wouldnt describe myself as a Hardcore rider, but I do ride in some fairly extreme weather sometimes.
My favourite three layers to add are a long sleeved technical top worn next to the skin....very breathable and wicks away sweat superbly so it cant go cold next to the skin, and good for travel riding as it has *ahem* anti bacterial properties and dries very quickly when washed in a hand basin of warm water.
second layer is what once was a very expensive lamb's wool thin jumper...it holds heat extremely well whilst being very comfortable and light. It's gone all bobbly now, but as a layer, it's superb.
I do have a synthetic, fairly fluffy jumper that does a similar job and is also light and packs small, but the arms are a bit short so this one often leaves my wrists getting cold.
Third layer is a windproof goretex walking jacket which comes down over my bum, has long sleeves with adjustable cuff-bands
Over the top of it all, I wear my trusty Aerostich one piece.
The goretex jacket helps trap the air in the lamb's wool jumper, but also prevents the occasional long distance leak that my now 10 yr old 'stich allows, particularly if it's an all-day ride in very wet conditions
The point where the 'stich will leak is in the groin and around the top of the chest area....mostly its down to me not getting the overflaps sorted properly, but the long walking jacket tucks in around my gentleman vegetables so even if I get a groinage leak through the 'stich, my tackle stays dry......and there's nothing quite as unpleasant on a long wet day than cold wet tackle
Oh.....If it's cold enough, I'll also add my home made heated body warmer (over the jumper but under the goretex jacket)
Gloves....BMW GS gloves over thin windstoppers, used with muffs.....winter gloves IME are just crap.
Muffs also dispense with all that fukking about with tucking everything in in the right order and keep my hands totally dry...that and heated grips, job done.
Socks.....Thin technical under thin(ish) long (knee length) ski socks
Kecks.....Rohan technical or similar.....NO COTTON kecks that would hold water and make your bits shrivel even more than they normally do on a cold wet day
Head......winter buff tucked under body layers and over ears, then in really cold weather, thin synthetic balaclava under helmet...rarely worn though now, as i had a nasty experience when it slipped when I did a lifesaver and I had one eye covered by it until I could pull off the road and sort myself out
