I do think the UK would be better off using 230V but not for power saving reasons. Because the UK's a relatively small market compared to the entire EU (or the entire former 220V market) the vast majority of appliances are designed to cope with 220-230V.
I've heard that there are issues with peak voltages in the UK pushing what are really 220V appliances beyond their designed upper limits e.g. increasingly electronic-laden domestic appliances like washing machines, dryers etc blowing when they're presented with a UK peak voltage...
It'd make sense purely to avoid all these minor problems..
