Hi Liam

I have never worked on one of these but,

check for crank sensor at ecu pin 55(blue yellow) and 56(blue green)

Check Ignition Amplifier
Pin 4 ign feed 12v (black)
Pin 6 Chassis ground (brown)
Pin 2 ECU coil turn on signal (blue red)
Pin 5 Primary ground circuit (green)

Check ign coil
IGN 12v
Primary current

Have you got a scope or a logic probe?
Make sure the ecu is sending the signal to the ign amplifier.

The fuel shut off switch appears to only have control over the fuel pump

hth
James