In the end I stuck with a sleeping bag. I can unzip it and use it somewhat like a quilt when warm, or if cold, zip it up and keep warm. For me I decided this was the best option.
Fyi I sleep like that, figure 4 with a alewpi go bag unzipped.
Timmermade makes something wider at the knees for this. But you'd need import from usa and trying to actually buy something from him/them is now impossible.
In the end I stuck with a sleeping bag. I can unzip it and use it somewhat like a quilt when warm, or if cold, zip it up and keep warm. For me I decided this was the best option.
https://www.reddit.com/r/Ultralight/comments/zg4tlb/quilt_in_uk/