Set Appliance State:

Mains Power Off
Gas Off
CH switch OFF
Ensure secondary heat exchanger is cool and requires pre-heat (this can be achieved by running the DHW with the gas to the appliance turned off)
Gas On
Mains Power On

Observation:

Pre-heat switch ON.
Allow fan to run and ignition sequence to commence.
Is sparking observed at the electrode tip and does pilot ignite?