I'm hoping there are some washing machine 'experts' here that might have
some suggestions about my washing machine problem. Basically it seems to
get stuck when it gets to a part of the cycle where it's supposed to rotate
the drum in the back & forth wash cycle.

I have done some debugging using a Haynes general washing machine manual
(although it's not specifically for this machine of course). Also, I am
electrically minded so I have a multimeter to check voltages, continuity
etc.

Depending where I rotate the Programme switch to I have determined that:
-The heater works. (water gets fine & hot)
-The (two) thermostats work. (Heater cuts out when it reaches temperature)
-Drum spins (when set to the spin cycle)
-Pump works (when set to a drain cycle it pumps out the water)
-Door Interlock works (cannot open door during eg heating)
-Inlet solenoids work (hot & cold fill let's in water fine)
-The Pressure switch works (as best I can tell). I disconnected it at the
drum end and blew gently into the hose. I could hear three distinctive
'clicks' depending on the air pressure I applied).

So now I'm looking at the controller (timer) which is an old mechanical
type. It has a single drive motor with a solenoid at the end. I believe
the little motor on it is running (I put a screwdriver up against it and to
my ear and I could hear a whirring sound). However the main programme knob
does not seem to turn (advance) as it should.

SWMBO also tells me we have had some intermittent issues in the last year or
so where the machine would get stuck on a cycle but if 'nudged on' at the
programme knob it would continue and it might not happen again for weeks.

So I'm thinking it's the Programmer/Timer I need to replace but they are
quite expensive (and a sod to remove/replace) so if anyone has any more
suggestions before I take the plunge I would be most grateful.

Thanks, James