James1809, your examiner is wrong. If she won't accept that, tell her to call the CAA!
You are right. Basically all exams can be credited within the normal validity and exam time limits; however, you need to pass FP&P
and navigation before 1 Sep or (in your case) you would need to take FP&P again.
The original IN was incorrect, so I persuaded the CAA to re-issue it in (slightly) clearer English.
It just goes to show what a desperate state the UK flying training industry is in, if students know the regulations better than some examiners....
Cobalt, ask that examiner if he's ever heard of Regulation 6 action....