Very much appreciate that vgorst!
I think I'll put the heat lamp inside the viv, and swap the two UVB bulbs for one Arcadia and see how he takes to that. I guess for now, paper will be the best thing until he's less stressed and is eating/growing properly.
I'll take the advice on the Nutrobal too, I have heard a few people I've talked to mention this so it must be good!
I'll make these changes, then decide whether or not he is shedding and if he is in need of bathing.
Thanks so much everyone, you've made me feel a LOT better about him, maybe I'll stop worrying now and leave him be
If there's no change in a good few days, I'll be off to the vets with him!