As you can see (on the already mentioned FCOM page) the system is in the closed circuit configuration and in addition the air it is in a (i would call it) closed loop. No air from the avionic bay area and no air to the cargo underfloor area. No system is 100% leakfree, so you have to add air.
Originally Posted by Bbow
... I pressume this air gets fed through the Air Con inlet V/V, from the AirCon Duct? And this Duct is obviously downstream of the packs? ...
The conditioned air inlet valve is installed in a duct which is connected to the cockpit main supply duct.
Location:
Edit: image added