Thanks. Sods law though, the boiler has started again now after it has been off for an hour or so. If it doesn't start again I will measure those voltages.
Has any one an idea how to sort my boiler out on a cold New Years day?
It has made this clicking noise before but a judicial thump has cured it and it has fired up. The pump runs and fan and pilot all work fine and then what should be just one more click as I presume the main jets of the gas...