Removal of electric shower and replace with “digital” mixer shower – any significant electrical work needed to “complete” the change?

I currently have an electric shower with cold water feed and its own "isolator" with a string pull outside the shower.

Looking to have it replaced (by a professional, so I'm asking more out of curiosity and to understand the process rather than to do it myself) with a shower fed from the hot and cold water tanks.

The setup is a hot water cylinder, cold water tank that feeds the current shower and the hot water cylinder. These tanks are on the floor upstairs from the bathroom.

Been told that to have a mixer shower we need one with a pump due to water pressure (lack of) between the tank and the shower.

I am now looking at "digital" showers with the temperature controller where you can set profiles, schedules etc.

I would like to know whether there will be significant electrical work involved in replacing this electric shower with the proposed digital shower.

• I'm assuming the "controller" for the shower still requires the electrical connection? (Mains voltage – this is in the UK so 240V)
• as such, do I still need the "isolator" string pull?
• can anyone give an easy to understand explanation of how the "digital" shower does its thing?
• if the current electrical connection for the shower is redundant, does it need to be "closed off" in some way?

As said above I am getting a professional involved not intending to do it myself, but would like to be somewhat 'in the know' when I speak to them!

NB: there is already hot and cold water to the bathroom for the sink and existing bath (which has the shower over it and will be replaced by just a shower cubicle). The cold water taps come off the mains feed (1 floor below) rather than the cold tank.