Excuse me gents for the interruption but Simon are you running a mechanical fuel pump? If so have you checked to see if the knock is coming from there? How about the timing chain and spocket. Do you have a stethoscope that you can place on different parts of your engine while it is running? Could your rods be bumping the bottom of the
oil pan?
Good luck!
Clois Harlan-Tulsa, OK (USA)