So after taking my aux belt off and letting the car run for a min, its quiet.
Once i put the belt back on and started the car it was fairly quiet until i flicked my lights back into auto (I had turned them off for when it was running with the aux belt off), the lights came on and it started making a noise again.
Hmmmm, strange.
Turned the lights off and the noise all but disappears. So its probably my alternator bearings which is a royal pain in the ass as i have just had the alternator off to change the pulley. Or its the aux belt tensioner.
Not sure if this will help any off you lot but its got to be worth a try.