oh hi, follow up on this.
Got a hold of Howat, except he was rather busy so was going to be a week before he could look at it.
So I phoned up Wellington Automotive Gearbox Specialists (used to be Miles Udy) and the joker Dave who runs it said to take him for a spin. So I did that and he said it sounded more like an axle bearing rather than diff related. He did mention that a diff rebuild with new bearings would be $800..
So I whipped out the axles with the help of Ricks beefy slide hammer (i tried fucking everything and nothing worked, two smacks each with that and they were out!) and dropped them off to my mechanic who cut off the old bearings and pressed on the new.
And now it is super sweet!!
Thing to note tho, when I checked the bearings the drivers side was grumbly, however I always thought the noise was from the left hand side.