It appears that the short bus has taken a detour and ended up here.
The distinction between challenging a potential subsequent fixed penalty and having a defence to the allegation are at best academic at this stage, and substantially drowned out by the absurd assertion that the OP would have a late/defective NIP defence.
Whilst the requirements to serve a NIP within the 14 days is mandatory, for offences that require a NIP - whether this one does or not is anyone's guess as the OP has chosen not to trouble us with the nature of the alleged offence, except where the statutory exceptions apply - same, the required details - time, date and nature of the alleged offence are "merely directory" - meaning that if such details are incorrect or unduly vague, it does not negate the NIP if the defect does not defeat the objective of enabling the accused to recall of identify the incident in question.
TL;DR - if the OP "knew" that the time of the incident was 7:34 not 8:34, putting 8:34 on the NIP does not invalidate it.
In the abstract, that would tend to raise questions regarding burdens of proof and strategy - whether the prosecution would need to prove that the accused was aware of the correct time (and/or the incident in question), and how to raise the issue without giving evidence (and therefore proving the prosecution's point for them). However, in this case, that ship has very much sailed.
Regardless of whether or not a NIP is required for this offence, or whether a statutory exception would apply, the police have evidence that the OP was not misled by the error, so it is not a viable defence.
As a matter of principle (and to avoid committing an offence under the Perjury Act 1911), as regards the s. 172 requirement to identify the driver, I personally would not be naming my self as the driver of vehicle A at time B and location C when I was nowhere near location C at time B.
The OP can either -
-play nice by confirming that he was the driver of that vehicle at the correct time, or
-play a game by correctly stating that the vehicle in question was not at or near that location at the time specified. If the police, who already know that the OP was driving at the correct time, but don't seem to be in a hurry to fix their mistake by issuing a corrected s. 172 requirement (generally in the form of a new NIP - but the NIP requirements do not apply, before anyone starts asking stupid questions). If the police then do what they should have done and issue a revised notice, the OP is basically in the same position as he would be in if he played nice, with the possibility of the police being less favourable with their response. Again, what that response is likely to be would seem to depend on the matters the OP has chosen not to trouble us with.
It is not immediately obvious in what way the consequences of a criminal conviction for the unspecified offence would differ from those of receiving a fixed penalty for the same offence.
