Hi @Lou58ise
This is a particularly British habit.
We use feather or hypoallergenic hollow fibre duvets with a cotton cover encasing them and a base cotton sheet covering the mattress and cotton pillow cases.
We sleep on the bedsheet covered mattress and the encased feather quilt directly on top of us.
We us only your dry cleanable thin quilt/bedspread as a cover, over the duvet in extreme cold or for decorative purposes....my thin quilt/ bedspreads are all cotton and therefore washed in my washing machine, if the guest has used them.
In fact us Brits tend to use mostly cotton or poly cotton items of bedlinen which we can pop into our washing machine and electric tumble drier rather than use a dry clean ending service which is expensive here in the U.K.
The base cotton sheet and the cotton duvet cover are washed and dried after each guest stay