Set Appliance State:

Mains Power Off
Set Multimeter to AC Volts Set meter to measure AC Volts
DHW Demand
Turn on the Hot water demand and make sure the cylinder stat is calling for heat
Gain access to the mains connector
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage at the switched live input (R) and the Neutral (N) connections of the mains connector.
Is there voltage at the switched live connection now?
Expect 240VAC