I always buy duvets from John Lewis.
Bought one from JL two years ago. The sort that comes in two parts, one a higher tog than the other. The poppers that held it together broke on the first separation so it went back. It also absolutely stank of duck….
Bought one from Feather & Black instead, much better system of attaching the duvets and it didn’t smell. F&B often have sales with quite large reductions.
However, after a post about down on here I would definitely look into the ethics of how it is sourced when buying again. Something that didn’t cross my mind at the time. I always look to buy free-range eggs and higher welfare chicken/meat, but didn’t connect this to buying a down duvet. Wool would seem a better choice in relation to this.