Logically, speeding must be a continuous offence insofar as it is impossible to exceed the speed limit instantaneously. The logical argument would then be that if you were exceeding the speed limit for 1 metre, 100 metres, a mile, or 10 miles, that would only be a single continuous offence - regardless of how many separate witnesses or cameras saw you do it. Arguably, if you were to continuously exceed the speed limit going from an ordinary road to a motorway, or vice versa, that would/could constitute 2 separate offences as the offences are created by different legislative provisions.
Logically, to argue that being caught twice whilst continuously exceeding the same contiguous speed limit somehow constituted 2 separate offences because you were caught twice would require some logical argument that elements of the same continuous offence somehow constituted separate offences.
There is an
obiter (throw-away, or not binding) comment in some High Court judgement to the effect that it cannot be right that a driver, having been caught speeding at the start of a journey would then effectively have a free pass to continue speeding for the rest of his journey - but that somewhat unlearned comment from an otherwise learned judge not only seeks to ignore the principles of duplicity and continuous offences, it ignores that (unless the police are too lazy to do any proper police work, and issue fixed penalties like confetti), exceeding the speed limit continuously for say 100 miles would be an aggravating factor to that offence - meaning that the driver would not in effect have a free pass.
Logically, it would be somewhat harder to argue that you cannot be prosecuted twice for the same continuous offence if the court are not satisfied that it was a single continuous offence. As a general rule, the prosecution's burden of proof is "beyond any reasonable doubt", and the defence's burden of proof is "on the balance of probabilities".
The fact that the website does not show you the money shot does not mean that the police do not have it. If you were caught by a camera and the police do not have the photo(s), logically they must have a very effective Ouija board in order to issue the NIP.
If you dispose of criminal liability for an offence by accepting a fixed penalty, you cannot subsequently [lawfully] be prosecuted for that offence (
S. 78(2) RTOA 1988). The cheapest way out - assuming that you can persuade the court, on the balance of probabilities that it was a single continuous offence, would be to accept a fixed penalty for one the the "instances", and then defend the other on the basis that the prosecution is an abuse of process/statute barred.
Please do not ask us what an unknown bench on an unknown day will decide.