I think I've got my bread mojo back! It had been lost during my enforced time away from flour and the oven (during residential school and then nights in MK).
You'll notice that I've changed the way I get the dough into the Dutch oven - I tipped the loaf onto a circle of greaseproof and then lifted that into the oven lid. The advantage is that I'm not hovering my hands and the proving basket over a piece of cast iron that's just come out of an oven where it's spent an hour with the volume set to very loud. It also means that I can 'bang' the proving basket down on the paper to get the dough out rather than faffing around trying to ease it out gently. I've yet to cut it but the oven bounce was good.