I've just noticed a point of order that needs correction:
“The NIP has been sent by standard delivery since 1994 and can be sent by 1st or 2nd class.”
No it cannot. Road Traffic offenders Act 1988, Section 1 (Requirement of warning etc. of prosecutions for certain offences.):
A notice required by this section to be served on any person may be served on that person—
(a)by delivering it to him;
(b)by addressing it to him and leaving it at his last known address; or
(c)by sending it by registered post, recorded delivery service or first class post addressed to him at his last known address.
A NIP sent second class does not meet the requirements of the Act and is a bar to prosecution for the offences covered. (NIPs are never sent second class for that very reason).
Have you checked your licence yet? You can do so here:
https://www.gov.uk/view-driving-licence
Do you know who the Registered Keeper of your car is? You may need to contact them to find out what they have done in response to any S172 notices they may have been sent. You should also check what details they hold for you.