I have heard excellent reports about Derek Davidson's 5 Day PPL Ground School and Exams. That may be one option.
The other would be to study using Thom / AFE books and the Confuser (don't use the Confuser as the primary means) and take the exams at your local flying club.
Ensure you take the PPL Application From with the Exam Results ensorsed onto it when you go to NAC in August.
Not sure how much Derek Davidson charges for the 5 day ground school but I know the exams are included. If you take the exams at a local flying club then you'll probably be looking at something around £25 per subject to sit the exams.
No extra exam required for the night qualification. Indeed that is about the easiest rating / qualification one can add to their PPL in that there isn't a written exam nor a flight test.