I think I have it working now.
My ECU was missing:
R137, R140, R28, R29 and C22.
I have not found C83 yet, so I don't know if I need to fit it.
I have gone through the build tests, and get 150mv across pins 5 & 6, and 0.445v between 1 and 5. So all appears to be fine. Next step, testing on a vehicle.