Well I did manage to get this fixed. For anyone interested the fan is accessible from the engine side of the dash. Remove the plastic ribbed cover just under where the windshield wiper motor is and then the plastic black rectangular box under that (three clips hold it in). In my case it was a "rectifier" -- or that's what my brother called it, that has come loose and was lying against the housing for the fan motor. Some well placed electrical tape and voila! A quiet running fan. Just what I need as we set a record temp of just shy of 37 degrees the other day (that's celsius for those in the US).
Lesley