Marc,
Buen Camino. I walked last February (Ponferrada to Santiago) and we had no issues finding accommodations. There are fewer fuentes (fountains) in the area you will traverse than other areas on the
Camino Frances, and winter limits the availability of one's that are actually in service, which means you might have to buy a bottle of water every once in a while. Even in the cold and wet, it is important to stay hydrated on the camino. I've walked the Frances 5 times, and the February start in Ponferrada was my favorite time of year on any of my other caminos. Our weather was generally pleasant with a day or two of rain.
If it helps, we stayed in the following locations once we got past Sarria. As others have suggested, these may or may not still be open, but I spot checked a few for my upcoming 6th one, and found the ones I've checked have been open.
Portomarin: Albergue Porto de Santiago, which was excellent. (22K)
Palas de Rei: Pension Palas - a little out of the way, but nice. (25K)
Arzua: San Francisco Hostel - it was ok, and near the church (25K)
Lavacolla: O fagar d' Maru - great host at her private residence (29K)
Santiago: Hospedería San Martín Pinario - fantastic. (10K)
We walked some longer distances like Ocebrero to Samos, and Samos to Portomarin in a day each, so some of these days may be a little long depending on your liking, but we found places generally open along the way. We liked the extra hike to Lavacolla leaving us only a short morning camino into Santiago, and depending on your time, would recommend that if you can. It left us with no worries to get to pilgrim's mass and to enjoy the beautiful city. If weather permits, make sure you walk the park overlooking the Cathedral, especially when at night, as there are few better views to soak in what you just experienced.
We are going again with an Astorga start on Feb 24, so we will be a few weeks behind you.