BA A318 Centre Fuel Tanks
 

Of general interest, but could anyone please confirm the position/location of the Additional Centre Tanks (ACT) on the two British Airways A318 aircraft; i.e do they take up what would have been hold space in the forward and/or rear holds?
Also, assuming that Airbus do not offer the A318 in a 'containerised' version, could anyone confirm the hold layout; is there an aft bulk hold?
Thanks for any guidance.