During low rpm, when releasing my clutch to take off slowly, theres a clickin noise of some sort which comes from under the car somewhere, sounds like its around the gearbox.

Even when the clutch is fully disengaged, it still makes the noise at low rpm, ie, around 1000 -1250rpm

But yeah you can hear it out in the street when you take off, but its heaps louder when in an enclosed car park.

Really annoying, what is it??

sounds very much like a seized uni joint best check it out asap!