Rusty wrote:
I realise that mixer taps are made a bit differently here, mostly to
prevent syphoning from the hot water tank into the cold water system
in the case of low pressure.
That regulation never seemed to worry the DIY sheds much. A lot of the
foreign mixer taps they sell have a one-tube spout and will connect the hot
and cold supplies. Perhaps its legal to sell them, but not install in the
UK?

It's (AFAIK) legal to use them in the UK, provided both H & C are from
the tank. Commonly called 'bathroom' mixers, as kitchens traditionally
need the two-pipe spout to keep the mains 'drinking' water separate.

Owain