We changed DS1(2.6) cot into a bed at the weekend. Transition all smooth, he is quite happy to sleep all night as usual but he is quite thrown by the idea of a duvet as opposed to grobag, to the extent that he will sleep sideways over his pillow rather than get under the duvet and he's chilly.
What's a good strategy to get him to understand the duvet and how long can it take to get the hang of it?