Thanks dc42. We have 415VAC here in Australia so that unit won't do but I will have a look for similar units.
Regarding the voltage monitoring; just checking that I've got it right.
The AC voltage connects to the resistor (lowering the current but maintaining the high voltage) and then into the rectifier (which has to be a high voltage unit). The voltage comes out of the rectifier as 240vDC (or slightly greater). Would it matter if the resistor was after the rectifier?
I can only find opto-isolators that take a low voltage to the diode and switch to a high voltage.
What I need here, is the reverse: An opto-isolator where the high voltage feeds the diode which is switching the low voltage.