Ok, have tried the duvet in it and it certainly reduces it by enough to be worthwile so it's a thumbs up for the Snugpak. My not very scientific measurement reckons volume reduced by about a third. One thing I would say though is that I only use a 4.5 tog duvet as I prefer being cold to hot and I think you would struggle to get a thicker duvet through the neckhole.
I'm sorted though, thanks for suggestions
I'm sorted though, thanks for suggestions