@Richard_Aus
the sequence of bleeding is IMHO wrong. Had similar problem on my RHD Plus 8 (2001).
Found in gomog manual that you must start at the front axle left side ('cause dual piston caliper) - then front axle right side - then rear axle right side and finally rear axle left side.
Repeat: RHD
Its different for LHD !
Axel

Advantage of hydraulic brakes: equally surface pressure all around (old advertisment of ATE)