Welcome to the Forum.
My instinct would be that all is not well with the hog for it to be coming out during the day, the same as it would be in the Summer. I have had a hog here all winter, but have never seen it out during daylight. I would be inclined to get it checked out, especially with the cold weather putting an extra strain on it.
You should be able to get the details of your nearest hog rehabilitator from the BHPS 01584 890801.
P.S. Hope you have seen about and signed, the Petition about the A24 trap and told all your friends about it.