Yea it was only making the noise whilst moving, didnt matter if clutch was in or out, and the noise sped up as I was moving faster (noise was probly louder when driving slow), noise was there whether in gear or in neutral and rolling and yes noise completely stopped whilst I was not moving.
I once had had a screwed diff / uni's in my old car and the noise was much like that, although it didnt sound like this noise was coming from as far back as the diff...