not sure how you wire up an immersion switch incorrectly , without immediate catastrophic consequences - maybe if the cable was partially trapped in the terminal block.
A smart meter on the gas should show at what point the tank has been heated up to the (daily) legionaire killing 60C, to avoid keeping it on for long periods and replenishing hot water you may not need
A smart meter on the gas should show at what point the tank has been heated up to the (daily) legionaire killing 60C, to avoid keeping it on for long periods and replenishing hot water you may not need