Contacted a member of bmwland.co.uk , who also works for BMW, and according to their ETK i have a GA6HP19Z autobox with the Q126 torque converter, this is rated to 400nm of tq.
Also the gearboxes are rated:
GA6HP19Z (designed for maximum torque of 400 Nm)
GA6HP19Z TU (designed for maximum torque of 400 Nm)
As stated here from BMW TIS -
Assumption is the mother of all ......