Hi Mark
It sounds as if the little one is a bit on the small side and also hasn’t been a regular visitor, so I would be inclined to contact your local rescue and take their advice. They will be familiar with the weather conditions in your area and you can explain the position more fully to them.
Putting a blanket over the box is probably not going to make very much difference.
You can get contact details of your nearest hog carers/rehabilitators by ringing 01584 890801
Good luck. I hope all goes well.
