You have received good advice from other experienced English colleagues. I am the AM of EA1, but I have hardly visited that area. They are mountain roads, sometimes very narrow and twisty, it takes a long time to reach some destinations. It is always good to study the terrain, the maps, see the experience of other mountaineers. Being the first is always a risk. The ideal is to have the GPS track and the comments of someone who has done that summit.
In that area I have only climbed Peña Bricia, EA1/CT-047. Fantastic landscapes, the final stretch can be a bit complicated. You should see my track. It is in sotamaps. But, from Potes you have an hour’s drive to the beginning of the route.
For the conditions you propose, I advise you to look for simpler summits, lower, with less points, but apparently simple. I say apparently, because, without more information, you never know what you might find. I suggest:
Pico del Valle, EA1/CT-133, never activated.
Pica de las Puertas, EA1/CT-115, activated once.
There are some more summits of that style in that area.
In the area of León, my territory, I strongly recommend Pica de Ten, recommended by Colm. It’s a fantastic one-hour hike, suitable for anyone who doesn’t have vertigo. Fantastic viewpoint over the Sajambre valley, but maybe a bit far from your destination.
Near Santander, indeed, the Picota, EA1/CT-101, must be easy because it has been activated so many times. You also have Peña Cabarga, EA1/CT-089 in the same situation.
The Bilbao area is out of my territory
Don’t hesitate to ask more if you need it. And enjoy. 73