Still riding to work. A proper leather jacket is good for safety, but a well designed one also will cut the wind. I can ride in pretty cold weather with nothing more than a sweater underneath because no wind gets in.
Secondary to that, you need warm hands. Get good, insulated gloves that are long enough to go OVER your sleeves. This will further seal out wind and keep you toasty.
I wear a fleece balaclava that traps heat and keeps the wind off of my face and neck. With a decent helmet (not a tiny lid) your head will be warm.
My legs don't get too cold with a V-Twin heater sitting between them, so long-underwear and thick jeans do the trick. Adding rain pants over that will take care of the worst days for me.
Finally, I use insulated boots with good ski socks. Have some room to move in there, same as skiing, ad your feet will be OK.
I generate more body heat than most, and carry a little more natural insulation than some, but that is all I have ever needed. Of course, once the temps hit freezing, I am off the bike. But in 40 degree weather, I am fine.