How to clean enclosure when he's never up when I am?

I am wondering the best way to go about cleaning my hamster's enclosure when he is only ever up after midnight these days.. he's morphed into a ghost hammy :(

His burrow is right in the middle of our Bucastate enclosure under a load of bedding and I am pretty sure he is peeing in there.. as he isn't peeing very often in his sandbath anymore and last time I cleaned his burrow out properly he wasn't a ghost hamster so it was easier!!

I can't seem to get him to come out by moving things about or offering treats as he is so tucked away from it all! How should I go about waking him up to put him in his playpen so I can give that area a good clean? I don't want to startle him too much, and tbh I really miss him even though I knew it was a possibility I might not get to see him much at all. I think my 10 year old is taking it better than I am!!