Sounds like the hog may need some help. The best thing to do is ring BHPS on 01584 890801 and they should be able to give you the number of other rescues. I would keep trying to get hold of one. They often have more experience of hog problems than vets do.
Meanwhile I would take the hog in and keep it in a box with torn up paper or a small towel and food and water. Please see further information: https://www.britishhedgehogs.org.uk/found-a-hedgehog/
Hogs are very good at escaping, even if unwell so use a high sided box or pet carrier.