The case for training through a British winter

Nobody’s motivation survives November on its own. The people still training in February are not more disciplined than you — they have just removed more of the friction. Most of that removal is boring and practical, which is why nobody posts about it.
Lower the start-line. The session that happens beats the session that was planned. On the worst days, the deal is: get to the gym, do twenty minutes, and you are allowed to leave. You almost never leave — but the deal is what gets you through the door.
Kill the cold-start excuse. Half the resistance to winter training is the ten frozen minutes between leaving the house and warming up. This is genuinely why the layers exist: a heavy hood over your kit means you arrive warm, train, and leave warm. It is not a style decision, it is a compliance tool.
Book sessions with another human. A 6am session alone is a suggestion; a 6am session where someone is waiting is an appointment. The data on this is embarrassingly one-sided.
Train at lunch if you can. In a British winter the only daylight you will see on a weekday is the middle of the day. A lunchtime session is light exposure, a break from the desk and the workout, all in the same hour.
Spring training is built in the winter. That is the whole pitch. Start now and April you will be unrecognisable to January you.