Thanks!
At the moment I'm just trying to let him settle into his new (albeit temporary) tub, but yesterday morning I found he'd pushed all the substrate paper to one end and I had to nudge him out of the way to set it straight. He felt quite cold after sleeping at the cool end overnight (22C/72F) but soon came to life when I touched him. I set the tub straight and changed his water, but he didn't act defensively at all so it seemed a good opportunity to take him out and check him over thoroughly. To my surprise he didn't even musk, he just gently cruised around my body taking everything in for about 20 minutes, then I put him back.
I'm reassured now that he's going to calm down more and more with each handling session. It also gave me my first glance of his iridescence in the sun through my window. Wow! Like a milky version of a rainbow boa. It's given me a couple of ideas for a name.
Today his tub looks fine so I'm not going to touch him at all, just take the lid off for a good change of air. The same again tomorrow as long as everything looks fine, then his first feeding on Saturday!