//The police are legally required to serve the Notice of Intended Prosecution within 14 days of the offence -//
Quite so, barry. Road Traffic Offenders' Act, Section 1. If AuntPG received the notice beyond 14 days she should have declined the course and fixed penalty and defended the matter in court. The difficulty she may have had is that the Notice is presumed served two working days after posting unless the contrary can be proved. If the prosecution can prove that it was posted in time, the defendant has to prove that service was not achieved in time.