I had been advised by a local garage that the wires inside the motor mechanism can get tangled on the drive wheel, so I completely dismantled the assembly, tested the motor (OK) so reassembled with new grease and the assembly worked fine, I replaced it into the door and the window went up & down when I applied a powrr supply from a spare battery with cables.
I still had the problem that there was no live feed to the rear door switch even when the engine is running. Looking at the wiring diagram in the downloadable worshop manual, the power comes from the fusebox, through the drivers door switch, to the rear door switch and on to the motor. In my 'fault finding' search to see where the power was failing, I found that after my dismantling and reassembly of the motor assembly it now works fine from the drivers door switch (a bit slow, but very acceptable), and the rear door switch is U/S.
So I had 2 problems, tangled wires in the motor assembly, and a broken rear door switch. I can live with this, as no-one ever sits in the back.
All done, thanks 1of1, and good luck to anyone else doing this job.