PNEUMATICS
Bleed air for the LE is fed via a tube with little holes which blasts onto the rear side of the LE think of it as a o (tube) inside a D (the LE) the bottom of the D has periodical open sections to allow the bleed air to leak out.
Now the LE AI cannot be used with the LE flaps extended as the LE gets protected from the relative airflow by the LE flap ie Retracted _D extended D\ hope you can imagine what I'm talking about, this would result in overheating of the LE and therefore the restriction.
There is one pre cooler in each pylon to reduce the temp initally for the bleed system and it's components.
Each pack has a heat exchanger it's actually 2 (primary and secondary) stacked on top of each other and appear as one unit the cat converter is at part of the pack after the ACM is finished and prior to entering the A/C I think from memory it's after the water separator, but could have that wrong.
ELEC
Two batteries APU and MAIN, will have to get back to you on details. (APU batt does more than just the APU it's a bit understated naming it APU batt - a hangover from the classic where it was solely for the APU).