Sven,
If you are installing single cores through a panel, you have to bring them in through a non-ferrous plate or gland.
This prevents Eddy currents from the wires inducing currents in the panel metal.
Over here we generally cut a large slot out of the metal panel and fit an Aluminium plate over this and then fit plastic cable glands into the Al plate.
You're right about the conduit entries.
We seldom use single cores over here, apart from on really BIG jobs (200-400A+ per Phase), it's a lot easier to run Neutral-Screened into a switchboard(it's round) and this is used 9 times out of 10!.
Not a silly question in the slightest.