Seeing as my original question (instant heater or electric shower http://forum.buildhub.org.uk/ipb/topic/1873-electric-shower-vs-instant-water-heater/) ended up being answered with 'neither- fit a UVC', I decided it would be better to start a new thread.
I know that these units are not a DIY install and that you need a plumber with a G3 certificate. They are also to be checked annually.
Just how much of the install needs to be done by a plumber? Need to know so that I can plan to
be at the right stage. I like to do as much work myself as possible so what is the minimum that a G3 plumber would do and be happy to leave me to finish off? I presume he will need the electrics in place, but what if I haven't finished building the actual bathroom and there are no taps or shower in place yet? Will he be happy connecting to pipes that I have already boxed in behind plasterboard?
I've also seen reference to 28mm copper pipes... I've only got a 25mm service void and my plan is to run everything through that- tight but doable in 15mm especially if I have no fittings boxed away anywhere.
I guess this will be a sort of Q&A with @Nickfromwales so will buy him a virtual pint...