Pillow and duvet for 9 month old

[Csimms]

Hi, my little one is 9 months old, he goes to sleep on his side, but during the night he turns onto his tummy. At the moment we cover him in a couple of blankets, one thin one and one thick one, depending on the temperature. No matter where I put him in his cot, he manages to move up so that his head is right against the cot bumper. when he moves around in his sleep he tends to knock his head gently but it disturbs him and he wakes up.
Was thinking would a pillow work and stop him from shifting around so much, but not sure if this is a good idea as he likes to sleep on his tummy - advice welcome please... Also when is right age for me to start using the duvet that comes with the bedding set with him?
Thanks

Pillows and duvets (as far as I am aware) should not be used for under 1s. (There is also some debate about the safety of cot bumpers)

I don't think a pillow would stop him moving anyway.

No, not a good idea, especially if he often sleeps on his front.

At this age we got a 6-18mo grobag and tucked the end of it under the bottom of the mattress. It didn't entirely stop him moving around, but did reduce the crashing into cot bars.

Alternatively - Airwrap might help?

neither are recommended before 1 year and it is recommended to remove cot bumpers when they can get up on their hands and knees as they could try to use it to climb out.

btw, the airwrap isn't like a normal cot bumper as it's breathable mesh, and gives way if it's pulled so couldn't be used to climb out of the cot.

(no, I don't work for them )