You can set the temperature on Citygas at 42 degrees(recommended). So your children will not get scalded. Storage heater is always maximum temperature, so you got to use the bath mixer to get the correct temperature.
I am on Citygas water heater now and I wanted to change to rain shower set but I noticed that the water pressure is low even on the normal shower head that I have now. So do keep us posted on the outcome on the rain shower water pressure.