Ok. After much searching forums I was none the wiser. There are instructions in the user manual to reset the auto and rollback functions but these didn’t
help.
The behaviour I had was
1) auto down worked
2) auto up didn’t work
3) manual holding the button to close the window caused the safety rollback to kick in just as the window got to the closed (resistance) position.
What did work for me was just pulling the window regulator connector out, cutting the power, with the window in the closed position. Then I performed the procedure from the user manual - lock the door with the key, lock again but hold the lock position for a second or two.
What went wrong initially? Well, I think that when I installed the new regulator, the position was set so that I could access the glass retainer clamps through the rubber grommets. This position would represent the window slightly open, so I think I connected the motor harness and the system powered up in the wrong position. Seems like you really need the window closed position when powered is applied to the motor. Kinda makes sense.
Now it all works! I love the engineering detail that goes into these systems.