There was a noise coming from the roof first sounded like a tap dripping but it turned out to be the whirly bird roof vent as it turned.
The whirly bird was over five years old and never had been serviced.
Seems like this is a requirement after three years.
Simply removed the top, gave the bearings a squirt or three of WD40 then put it back to hear the sound of a silent whirly bird