Tried a different tactic with Cay tonight.
Last night he was in just a nappy, and he woke in the night fidgeting, I think because he was a little cold, so I lifted a blanket over his legs and he went back to sleep until he kicked it off.
Tonight, I've put him in his nappy, in a bag.
I've poppered the bag over his shoulders and under his arms, but left the zip open so his legs are still nice and airy.
Seems to be working so far... Xx