I was under the impression that you couldn't do the night flying until you'd done a certain amount of P1/ut time under the PPL syllabus - obviously, you'd need to be able to go solo! (however there may be no requirement).
Aside from using lit structures or roads for night VFR nav, it's not much different with a better instrument scan required - take offs can be interesting when it's pitch black with no visual cues.
But night flying is great fun - quieter, smoother mostly, and visually stunning - nothing like landing on a nice big runway with all the lights on - very cool!