Best setup when adding 2 new shower rooms (pressure, temp, flow, etc)

[benny269]

Hi all

New to plumbing but about to undergo significant renovation at home so looking to get well versed in the language and get some advice about what would be most suitable in our situation.

Current setup has a water tank in the loft and a cylinder in an airing cupboard. I'm not sure what you would call this system but I believe it is an immersion heater. It's the same central heating system since the house was built 30+ years ago and since we've never had any problems in the past previous advice has been to keep it as is. (Other than replacing a pump and flushing the radiators, everything still runs great.)

Work on the house is intended to move from 1 bathroom upstairs and 1 toilet downstairs to 3 shower and toilet rooms, 2 upstairs and 1 downstairs. Ideally looking to change as little as possible because of reliability but concerns are as follows:

1. Pressure - Will the current system be able to support all 3 showers? I would want at least 2 (if not all 3) to be usable at the same time. I've heard/read about Megaflows, booster pumps, etc but I'm not sure of the pros and cons of each now which is most appropriate for me.
2. Heat - What would need to be done to make it possible to have hot water run comfortably in all places at the same time? At the moment if someone is showering upstairs and you open a hot water tap downstairs the shower goes cold.
3. Electric - Is it sensible to switch all 3 showers to electric power showers? Having to remember to set the water to heat works fine but has caused problems before when someone forgets to do that or too many showers in sequence uses up hot water faster than it can be heated.
4. Thermostat - What's the ideal thermostat in terms of bang for buck? We currently have an analogue dial programmer (on/off timer) in the utility room and a thermostat (temp setting) in the living room. It seems to make sense to bring these together, I've heard the hype about Nest and read some good reviews of Inspire but don't know any actual users.
5. Immersion heater and system - Is it worth keeping as much of the current setup as possible? All the advice I've had to date seems to suggest this so I've never considered any alternative. Perhaps now would be the time to do that.

Ultimately I'm looking to have as many showers have high pressure, plenty of hot water and able to run simultaneously as energy efficient as possible without sacrificing current reliability. If I'm not asking for too much!

As I say I am new to this so any information is welcome but I'm happy to get more specific about the current setup as needed or go away and read good resources if you can direct me. Any help is greatly appreciated.