In Oz it's a smidge more logical. Although it's been a few years since I've done them.
You do the PPL exams for the PPL.
CPL exams for the CPL. (Tend to do more "CPL" stlyle flying in Oz. In it is stuff on light twin ops, piston engine aircraft sysems, low to medium level met, no world stuff)
ATPL subjects after the CPL.
Each step is a building block. The exams are relevant to the licence you are after.
The IR is a separate paper (computer thing??). Highest pass mark required. 80%.
Nothing stops you from doing the exams when you want to do them and as far as I know they don't lapse. (Although the IR paper might.)