The gearbox is out again at the gearbox place and they say the chain is good and definitely no play to give it slap against casing.
The car was up on the ramp with the wheels running and when the power went on there was deffo a banging/ clunking towards the rear of the box I think it was around were the vc is. Car has near standard power 240bhp.
Its got to be something to do with the 4x4 system as when the vc was burntout and only running 2wd it was fine with no noise.