Let me explain. I'm used to what I now assume is the North American way of making a bed. You have a bottom sheet, with fitted corners. This is followed by a flat top sheet, then the blanket. This has several advantages, but the main two are that if it's hot, you can take the blanket off, but still have something over you in which to wrap yourself; additionally, the blanket stays cleaner and thus requires less washing, as it never really comes into contact with those who are sleeping in the bed. I realise you then need to wash the top sheet more, but it's a lot easier than wrestling with a duvet cover.
So why do the British omit this sheet, putting the blanket right on top of the bottom sheet? I have no idea. Maybe it's a cost saving thing, maybe it's because it rarely gets hot enough to only have a sheet rather than a blanket. I dunno. It's a puzzlement.
