If there's good reson for a delay beyond 14 days, ie postal strike or change of address, fair enough.
But, if an envelope arrived 8 weeks later, with a recent postmark, I think you'd have reasonable grounds to tell 'em exactly where to jump off.
Might pay to visit :
http://www.pepipoo.com/
Loads of info on there
NIPS are no longer sent via recorded delivery.
You might be worrying over nothing. Chief Constable's current guidelines recommend +10% of the posted speed limit + 1 MPH to allow for speedo error before passing on to CPS for prosecution. It isn't legally binding but considered best practice for police + community relations.
So if the posted speed limit is 70 mph you're generally OK at 78 mph. 79 and above and you're likely to be prosecuted. But often times the camera is set at 5 or 10 mph over the limit for ease of setting - depending which is more practical for the posted limit.
EG. In a 30 mph zone there is a guideline tolerance of 34 mph - so the camera will be set to 35 mph. In a 40 limit the tolerance is 45 so the camera ought to be set to go snap at 46 mph but to 'round' things out it might be set at 50 mph. You can't rely on that but there's a camera near me where that appears to be the case.
Finally, all vehicles produced since 1992 (I think) have to comply with
European regulation, ECE-R 39, stating essentially that the speed indicated must never be lower than the true speed..." In practice most vehicle speedos over read by 7 - 10 % of the true speed. In other words are telling you that you're going faster than you actually are. Combine that with the margin Chief Constables allow for and the chances are you are safe - unless you were really nailing it.
A long time ago I was sitting in a dealership chatting to the manager when an old boy on a FJ1200 came in. He was a regular there as well and he strolled in saying he'd received an NIP for speeding on the motorway and was probably going to get banned.
I'd followed him a couple of times and I'd found him a very steady, cautious, 20-25mph around town sort of rider. Plus the fella must have been 80 to a day!
As such I offered some encouragement by suggesting it would be very unlikely he'd actually get banned unless he'd been travelling in excess of 100mph.
"What speed were you actually recorded at, " asks I.