Thanks, I'll try that when I order some more parts from my supplier - unfortunately I don't have any electronics shops close by so I have to mail order - but I have to admit I don't understand how the zener could affect the output in that manner. You must have gone into a lot of trouble duplicating my circuit exactly but I note you've omitted the 470Ω resistor on pin 9 - is there a reason for this or is it a mistake? Also, the 1μ cap on pins 3 + 4 has become 18μ.
I like the idea of a separate (47kΩ) resistor in series with the variable pot to avoid sending the meter off the scale presumably.