if you can't keep warm
take the train until you can. Being warm and comfortable is essential.
Winter is the season of Gortex - it drives moisture out from the warmth to the cold and the drier inner layers keep you warmer than moist layers would. I find my old Hein Gericke Goretex needs its thermal linings in and optional bib attached to the trousers when it gets much below freezing, but with just a shirt underneath this kit has worked well down to -11°C! The only problem is when you take it off wet, as once you remove your core the moisture will even out again - put it on clammy and it takes about half an hour for body heat to get the moisture pumping back out again.
Silk helmet liner / balaclava if it's below -5° too.
Best tip? Wrap yourself around the heat of a sports bike and keep yourself out of the wind.
AlpineStars SMX4/5 waterproof boots keep my toes cosy enough.
Remaining problem as the years go by, winter gloves are not enough, phase change materials are okay for 10-20 minutes only, even heated grips are not enough either. Cheap silk inner gloves help but waterproof over-gloves or handlebar muffs really sort out the wind chill and then all is toastie.
In my experience on an upright naked, anything with with off-road aspirations (coldest bike ever - GS650 xcountry), or even a faired adventure style bike, you get much more wind blast from head to toe, especially thighs, belly and shoulders, and you need to pile more layers on to keep warm and safe.