I think the best thing to do is stick to some proper hedgehog food – especially if you have a problem with cats visiting. Hopefully, as they are specifically designed for hedgehogs, they will provide a good balance of nutrients. The food I use is called ‘I love hedgehogs’. The hogs here have been happily eating it for many years. Last year 12 hoglets appeared, so they seem to be doing alright on it. I get it by mail order, when I get food for the birds. Most cats don’t seem to take any notice of it. I think there is another similar type of food (with similar ingredients) made by, I think, Ark Wildlife, which apparently cats also don’t bother with. Because they are dry or semi moist foods, it is even more important to offer a bowl of water to the hogs.
I tend to put cat/kitten biscuits out only when I am watching – in a separate bowl so I can take it in – to help them keep their teeth clean! Some, though not all, of the hogs eat them. If a cat visits it is usually quite easy to scare it away. I find they don’t usually seem to try to get to the bowls if there are hogs there anyway, but the cats, being a more visual animal, are more sensitive to movement inside the house than the hogs are.
Good luck, and happy hog watching.