If at all possible, catch him and weigh him. 450grams is minimum for hibernation, but the heavier they are the better really. You can also call BHPS (number at bottom of the page) who can hopefully put you in touch with local carers and help you work out a way forward. Not all hedgehogs will hibernate- or may be active on different nights- I saw one last night myself, so if it’s a good weight and you don’t have any other concerns I wouldn’t be too worried, just make sure you are providing plenty of food and water. But if it’s underweight or you notice any potential health concerns please take it in and get advice. Keep us posted on the forum as well please.