Yes, it is warm at night and I do tend to stick my feet out of the bottom of the duvet but generally it’s OK. We have two sets of windows in our bedroom which we open and I also open the windows on the landing and in the bedroom beside us to get a bit of airflow, which seems to work.
Funnily enough, we’re still on a 9.5 tog duvet as Mrs. B is a cold mortal! Not feather, though, as I’m allergic to them.
I think the only time I’ve really suffered with the heat in bed at night was a couple of years back visiting the wife’s sister in South Carolina. It was generally in the high 30s and very humid during the day, and neither dropped much at night. The ceiling fan was a godsend then!