When the shower is at or above the level of your cold water tank, there are simple and safe solutions to turning the pump on and off as and when you need it.

The automatic ShowerPowerBooster relies upon a magnetic water wheel which will turn when the flow reaches 1.5 litres a minute. The hall detector in the solid state flow switch detects the wheel is turning and the pump turns on, the pump turns off when the wheel stops turning.

When you cannot use an automatic pump the choices are:-

A switch on the wall or ceiling (pull cord)
A simple on off switch where you plug it in
A 3 pin plug socket with a radio remote control to make switching on and off easy

Use an existing light switch or ceiling fan switch?

Things are simple as you can put the switch on the 12 volt direct current side of the transformer which is so safe, you do not need an electrician.

The best way to control the on on/off for use with an electric shower or combi boiler is to make it come on at the same time as the electric shower or combi boiler is switched on using the same switching as the combi boiler or electric shower.