Well being a glutten for punishment, I have all 16 mosfets for the main board on there way to me. The postage and customs and UK VAT cost the same as the parts! As could not source them all in the UK.
Curious to see if replacing all these brings any of the board back to life.
Will update with progress or lack of when I get and fit them back 😉
Next while I am waiting as I will clean up the old ones to read on a meter see if any obvious internal shorts on the original fets.
Update:-
Tested the SIZ342 Power Mosfets and 4 of the original 12 are reading short circuit.