Thanks for the comments guys - we PVA'd all the wood parts and bought some chew toys that attach to the cage bars, plus some hanging food treats and some nutrient stone things..
We also rejigged the layout a bit so the shelves are much lower down, then laid trails of food around to show him the way to things and added his burrow box from his old cage along with some of his substrate (and a load of his poop in his new poopenhausen!) - while we were doing all that he had the run of the ground floor in his ball so he had a nice run and explore (and a pee .. in Amy's hand
)
So here he is, exploring his new home - he seems bright as a button and he's explored everywhere already (he's only been in there an hour!), found all his houses, eaten some food, drank water, had a sand bath and, I think, pooped in his WC..