I took a similar line at AIB and fortunately didn't end up in your situation. However the two guys in my entry who did accept the offer as O (when they wanted and had passed P) both left the RN relatively early. The RN also promised a great lad in the entry ahead of me P but only if he went fish head first. They didn't keep their promise. He left and rejoined as P.
You know what the answer is. Call them and say that you are not interested. They'll come round.
If pushed for something profound tell them that with high O scores and a pass at pilot you are perfect for F-35. Good luck, don't kill off your dream before it starts.