I buy Fogarty quilts from Dunelm and have various tog ratings.
I like Fogarty for a number of reasons...they’re synthetically filled, very lightweight, have very soft covers, are very reasonably priced, and are bright white. I don’t use quilt covers, just a sheet between us and the quilt, all my bedding is white so the duvet just looks like a counterpane.
The thickest one we have is 13.5 but we rarely use it, 10.5 has been warm enough for the last number of winters but it depends on how cold/hot you are in bed.