These are shots from my own garden to demonstrate the type of environment that hedgehogs prefer.
View 1, the overhanging shrub gives them cover
View 2, quite a lot of vegetation, especially good for finding slugs and snails
View 3, same location, different angle. There is a little house hidden under one of the bushes.
View 4, another little house hiidden under a Hebe further up the garden
View 5, hedge and trees providing dry foliage for nests and places to find insects, grubs etc.
View 6, Ivy and bramble etc in the hedge, more cover and dry foliage etc
View 7, compost bins which contain worms, slugs, snails and other delicious titbits. The hedgehogs can crawl under the edge of the bin as I have not set it right in th ground as it should be. There is also a bird feeder in that area where they can glean seeds and nuts the birds have missed.
View 8, the pond, which has a bed of Irises on to which a hedgehog can climb to get out but there is also a little bridge of mesh just under the surface of the water. It is folded thickly so as not to catch in the prickles.
Hedgehogs may well come and drink from water features so PLEASE, if you have one, do not clean the algae off with bleach or similar substances. I lost a hog this morning and I am pretty sure this is what had happened to it.
Normally I do not release hedgehogs into small walled back gardens as they like to roam a very long way every night, however, sometimes they may have a slight disability that could put them at a disadvantage when meeting a predator but they are able to live totally normally. In cases like this I release into the Mencap Walled Garden at Stackpole. It is 6 acres and full of polytunnels, raised and sunken beds, soft fruit, flowers, vegetables and a secret garden. They have been breeding there so they must be happy there. Their web-site is being re-constructed at the moment but, using this link, you can still get a very good idea of the lovely place that it is.
If you are able to create a good environment in your own garden and there are hedgehogs in the area, why not encourage them by installing a feeding station? I have recently made one out of a plastic, underbed storage box. I cut a hole in the narrow end for the hedgehogs to go in and put the food at the end farthest away so no fox or cat can drag the dishes out. A weight on top so the box does not blow away or become tipped over by a fox, or push it under a shrub and just wait and see.