Well, I thought I'd log the outcome in case it helps another member
Took the fan off. It ran smoothly off the car.
Lubed it to death with spray grease, WD-40 and anything else I could find in the garage.
Put it back on and fixed the shroud to the cast ally landing panel with a few rivits.
Still noisy.
Drove the car 200 miles following which the noise stopped completely and a/c fan now as smooth as silk.
Methinks that heavy lubing followed by mucho vibration allowed lube to do it's work.
Another (very) low cost repair.
