OK. Tested last night and there seems to be plenty of torque. I did notice that I can push the spindle back about 5 to 6mm. It returns immediately, so I assume the spindle floats or is sprung along its length.
One thing I did notice during the procedure. I let the system cool down by switching everything off and with the MV port in the CH position there was some heat (warmth) emitted from the MV housing. This is clearly coming from the electrics (motor/electro magnet?). To determine if this is normal I switched the MV into the HW position via the timer, turned everything off and half an hour later no heat.
It seems when the valve port is in the Central heating position, even with everything switched off, the motor/electro magnet? requires power and is generating some heat (nothing excessive). Is that normal?.
Mark
PS. The water from the bleed was not an issue, but more than a few drips. Half filled a paint roller tray after about 3 minutes.