pilot 16, double check this if you wish but the expiry date on the jar ppl exams is as follows:
air law passed 1/1/02(example) you have a period of twelve months in which to complete all gound exams and for the CAA to have taken receipt of you application for issue of your PPL.
ONCE YOU HAVE REACHED THE ANIVERSARY OF THE FIRST EXAM IE 1/1/03 YOUR FIRST PASS WHICH WILL/SHOULD BE YOU AIR LAW WILL EXPIRE AND WILL NEED TO BE RE-TAKEN, thus each exam date reached without issue of your ppl will require a resit.
Hope this helps and GOOD LUCK!