Hi, I’m sure someone knowledgeable on this site will give you their advice, but, if you are designing hedgehog houses, they generally need a revamp. I bought a lovely one with DIY put together. It had a tunnel, essential, but they also need to have corridors inside, with turns, to deter cats getting in to the main chamber. Perhaps the tunnel actually needs a turn in it as well. A removable lid, but screwed on. Above all, it needs to be at a reasonable cost. A lot of people are elderly or children and not in work so can’t afford high prices, which I’m sure very good ones cost. The food we buy costs quite a bit as has been on the forum many times, so cost is everything. Good luck with your project and best wishes.