I'm very sure it's not the radiator fan as the noise increases with a few revs,, and the engine isn't over heated.
I was on the ProDrive day today and asked one of the instuctors if they had a similar problem with the ST after ragging,, err,,, high revving. I was told that it was indeed the steering pump. The oil gets hot and the viscosity changes. It's not dangerous
I think i'll put it to Ford service centre and see if they agree.
The noise does disappear a few mins after normal driving.