I had this problem too.OH has a mummy (tesco) bag and I used to have a duvet from blacks made out of sleeping bag material. It was ok but have been cold a couple of times so this year brought a proper sleeping bag. I too am wide (as my 6 yr likes to tell me) so I brought the outwell contour XL. It kept me lovely and warm in May. It also has a zip you can undo at the bottom to let your feet out, that's why I never used to like a sleeping bag before.
It says it's grey but matches my nevada M well.Pricematched in Go Outoors for £29.99.
I can't get on with mummy bags as I'm one of those who moves around a lot. Having bought a Gelert Pod XL I find it ok as there is some room to move but its not nearly as good as a double square bag, main problem being the taper towards the feet end. Additionally the inner material doesn't feel particularly nice.
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