yes the shower must have some form of switch control, other than the on/off on the shower itself.
there are rules for the distance of the switch and it must be a pull cord because your hands will be wet ,if it is in the bathroom
because they arent electric showes, they probably come from mains. You'll find electric heats water up as it comes out whereas yours are connected to mains and you have to have hot water there before you can have one gina
MIne has a 25 amp switch by the bathroom door which is 8' away from the shower. Installed by a qualified sparky over 10 years ago. I frequently forget to switch it off after a shower and SheWhoMustBeObeyed growls at me.