Hi Cadfolkhogs
I think it would be a great idea to make them a hog house. When so many people have such ‘tidy’ gardens these days, it isn’t always easy for the hogs to find somewhere they can make a nest – so hog houses offer them more options. But no you’re right not to disturb them. If they have found somewhere to nest that’s great, but they do move nests so will need somewhere else, too.
If you have a hog house, the hogs don’t always move in immediately some won’t until it becomes ‘part of the furniture’. As important as a house is nesting material. To them the house is only a structure within which they can make their nest (although some will spend days in boxes without making a nest, in the Summer). But to encourage the hogs to use the box sooner, put a handful of nesting material in the box to give them the idea and leave some piles of medium sized leaves, long grasses, etc. nearby, which they can use of they choose to. Hogs normally prefer to do their interior decorations themselves!
There are some instructions for making a hog house in the following, but there are other designs as well with interior ‘corridors’. https://www.hedgehogstreet.org/help-hedgehogs/hedgehog-homes/
Good luck and happy hog watching.