Well this extractor fan kept us awake last night.
I’ve taken it out of the loft (obviously) and there is some arcing on the circuit board that was causing it to power on/off every 5 seconds.
Looking into the Fan in more detail there is a fundamental flaw in it’s design in that the wires that run the power to the motor go through to the central vent which means that moist warm air can easily reach the electronics.
That’s Italian design for you.
So I am drying it out in the airing cupboard, will hot glue the part that allows water to get to the electronics, and then fix the arcing on the circuit board.
I guess this is one of the joys of home ownership.