Hi thanks for your reply, this seems the likely answer.
I assume that the temperature actuator is the unit situated behind the
temperature control knob is this correct ?
I have checked out the thermostat with a vacuum gauge on the vacuum
pipe by the on off tap, and this seems to function correctly.
I've actuated the tap manually, but this seems to make no difference,
to the temperature so I've ordered a new tap.
Will let you know what happens when its fitted.c