Well it seems clear that the council have acted correctly in issuing a Reg.10 after your driveaway. You have only two possible avenues of approach to representations, (1) mitigation - your wife in A & E, your short time parked etc or (2) put the council to the test that a PCN was in course of being prepared when you drove off.
Frankly, I think this latter is a doubtful approach. However, it's the only approach that will get you to the Traffic Penalty Tribunal, because Option (1) is based on mitigation, which adjudicators cannot rule on.