Nothing about winter in a well-built compact house is difficult. It is just a short list of things that have to happen before it gets cold rather than during.
October: the water
Check the trace heating works, confirm the drain-down valve turns, and lag anything in an unheated void that is not already lagged. A frozen pipe is the most common winter failure and the most completely avoidable.
If the house will stand empty, decide now whether you are draining it or holding a base temperature. Both work; deciding in January does not.
November: the envelope
Walk the outside and look at four things: the sealant around the windows, the lowest board of the cladding, the gutter, and whether anything is stacked against the wall trapping moisture. Twenty minutes, once a year.
Clear the ventilation terminals of leaves and check the condensate drain runs. A blocked condensate outlet in December is a water leak in a wall cavity by February.
December to February: humidity and heat
Keep the ventilation running continuously rather than boosting it occasionally. Continuous low-rate extraction is what keeps the humidity below the point where condensation forms on the coldest surface.
Resist the urge to close the trickle paths to save heat. Heat recovery already keeps most of it; sealing the house up is how you get mould behind the wardrobe.
Snow, if it settles
A shallow roof holds snow rather than shedding it, which is fine if the structure was calculated for the local load and a problem if it was not. Ask for the figure when the house is specified, not when it snows.
Clear snow away from the base of the cladding and the terrace door. Standing snow against timber, melting and refreezing, is harder on a facade than rain.
March: what to check before you relax
Look at the same four envelope points again, replace the ventilation filters, and check the loft for any sign that condensation formed over winter. Damp there is the earliest warning of a ventilation problem.
Note anything you found. A one-page winter log is what turns an unexplained problem in year five into a five-minute diagnosis.