There's a very low risk of sea ice forming in the Western channel, and Port de Chantereyne Marina, Cherbourg is tidal with a large range so not much risk of a layer of fresh. Therefore the risk of ice forming in the drain is reasonably low unless you have a flat calm after heavy snow fall.
If you are on shore-power, you could get a pipe heating tape kit https://www.tlc-direct.co.uk/Manufactur … index.html or similar to keep the pipe and seacock from icing up.
The other thing one could do if not on shorepower is to get some soft closed cell foam strip, somewhat narrower than the drain fitting and seacock opening, and stick a few strips together with the last one back to back so there's no exposed sticky to get a cross section of about 20% of the drain opening area. then mouse it right through the drain. If it does freeze, the foam should crush enough to cope with the 8% ice expansion.
It would be advisable to make sure the hose is armoured rubber in good condition, not old PVC hoze which may be brittle enough to split easily at low temperatures.
However for peace of mind in a hard winter, consider shutting the seacock, plugging the drain, rigging a temporary automatic bilge pump in the cockpit, and a low ridge pole from the hatch to the back cockpit coaming, with a tarp tightly laced over it as a cover.