Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Gain access to PCB (use Insulation Mat as required)
Disconnect ignition lead from PCB and make safe
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Tap reset button to skip self check.
WARNING : Stand clear of appliance during test.

Shortly after the fan begins to run can a strong consistent spark seen
from the spark generator to the spade connection opposite?
Note:
Boiler will attempt to light three times before going to ignition lockout,
it should spark for around 10 seconds at each attempt
with 1 second in between each attempt.