Meanwhile, back at the thread....... I have a very similar question, except that I'm thinking of replacing a Mira Sport 9.8KW shower. The water inlet comes in behind the shower, not from underneath nor above (I believe there are several ways of doing this). It has 10mm cable, a pullcord and RCD on a dedicated circuit via a submain and Henley blocks, so there's no issue with upgrading the electrics, just the shower.