My understanding is that under JAR, a night rating doesn't exist - only a night qualification.
What's the difference? A rating requires renewal and the qualification doesn't. Hence the disappearance of the old 5 to/ldg bit to keep the night rating current. The only thing you require to be PIC at night is 1 of your 3 Ldgs in 90 days to be at night if you want to carry pax.
LASORS E4.1 confirms that a night qual can be carried out during training for a JAR PPL, so there's no problem with what you're doing!