Right. Got an update. After not finding the offending click on the inside, I went and took out the blower. What a pain!! Found...nothing!! Got very annoyed and decided to pack up and move the car. Had one more look once I'd moved the car and noticed that one of the ducts was lose that feeds into the centre consol. I pushed it back and hey presto, the click went!!
So my new guess is there's something inside the ducting that's catching the inside of the duct. Can't see what but I do seem to have control of the noise!!