If the AirQuiz is the same website which I took out a subscription to then I wouldn't bother. The questions in the database point to the old syllabus.
The PPL Syllabus has been revamped under EASA.
I would use the Air Law books - Jeremy Pratt or Pooleys whichever you are comfortable with. Follow this up with the A4 Sized Revision Guide for EASA. They are around £9 each. This will help consolidate what you have learned and any gaps in your knowledge.
Scoobster