Hi jolerrs
Hedgehogs do dig a bit, but I’ve never had what you describe here. When I have seen hogs eating worms, they wait for the worm to come out or almost out and pull it out, rather than digging for it. Do you by any chance have squirrels around?
You could try searching for ‘Images for what is digging holes in my garden at night UK’ on Google (or other equivalent) and see if any of the images are similar to what you have found.
Good to hear you are getting a hog house. You might need to take additional precautions to stop a cat going into a hog house if there’s food in it. Many cats seem to manage to get into hog boxes quite easily. A barrier to block the angle of entrance sometimes helps, or a heavy obstacle right opposite the doorway, with only space for hogs to get through, but you might need to go to further lengths – depending on how persistent the cat is!
Good luck – I hope you manage to solve the mystery of the holes in the grass!
