Whilst I had the scuttle panel off for the water leak issue in my other thread, I checked the fan. Couldn't feel any noticeable play in it, so squirted some silicone spray onto the upper part of the spindle/bearing, to see if I could stop the irritating chirping!!
And hey presto....it seems to have worked!!! For now at least
If I can sort the leak out first, I may take the fan out for a proper clean and lube the bearings with oil at some point
So that's two good jobs I've managed to do this evening!!