Can someone please tell me what is required for a JAR-FCL PPL holder to fly an aircraft at night?
In a word - carrots!
A more in-depth answer (for the UK at least) is available in
this and
this section of LASORS.
A UK JAR PPL with a Night Qualification flying in the UK can fly outside CTRs and can make visual approaches.
Just noticed you're in Ireland, so you may want to read
this thread where I asked about night flying there. A consensus eventually emerged.