I did not see any ground leads on the supply or inside the lamp fitting, this would be a requirement if your bathroom circuits are protected with an ELCB.
Yeah saw the same thing, would always do that in a bathroom esp with chinese PSU.
Although the fixture is hanging outside reach it is good practice, but I do not know what the australian rules are in this case.
Concerning T4, never before heard of it, T5 is pretty much the standard here and you can see that there is less and less supply (and demand) now led is gaining ground.
And still the TCO, Lumens/Watt and lifetime of TL's is still pretty competitive with 20000 hours lifetime for the TL tube itself and 80000 hours for the electronic driver (or iron copper ballast if you wish) and only €2,50 for a replacement tube LED is way way more expensive.
The lifetime of the tube is influenced by how many start/stops you make but the same is true for the led electronics