Mags22 - " ... I'd be interested to know if one each would work ... "
I remember a good forty years ago when duvets were still called 'continental quits' and virtually unheard of in this country.
A friend of mine who had lived in Germany for a while swore by them, and bought two single ones over for him and his wife in their double bed. The Europeans always used them this way, double ones were only invented when other nations fought shy of the singles, and wanted a double size.
So in theory, two singles should work out fine - although like everyone else, we have always used doubles.