Hi nsp24
Well done your son for helping the hedgehog! I would be inclined to get it checked out by a hog carer, or at least take their advice before releasing the hog. You/your son can explain the details more fully and they will have the opportunit to ask any questions.
But when the time comes to release it, it’s best to be released back where it came from or in as near a safe space as possible – that will be the area that the hog is familiar with and so it will be likely to do best there.
310g sounds ok for this time of year. There is still a while to go until most hogs hibernate.
You can get contact details of your nearest carer by ringing 01584 890801 (no. also at bottom left of this page).
Good luck – hope all goes well.
