Best Route to Calais in January?

We will be driving  back to the UK (via Channel Tunnel crossing) mid to late January.  We usually do the drive from Calais with two stops - Poitiers and Zaragoza - using the N134 in France up to the tunnel through the Pyrenees then the E7 down from the tunnel in Spain - we usually avoid the toll roads.  Is there a better route that people use for winter travel when there may be a lot of snow in Northern Spain? Some people have said that Spanish roads are generally kept clear. Happy to make a couple of stops on the route.