I will advise him to check with his company to see the date stamp of the very first NIP to see if it falls within 14 days or not. Appreciate that he's only defence is a memory of the speed not being displayed on the digital board, so nothing tangible at all, if we presume he was right in that regard, how would one even appeal these?
Nothing to appeal at this stage. After he responds naming himself, he will be offered a speed awareness court or a fixed penalty (£100 and 3 points), assuming he is eligible.
If he does not accept one of those offers, he will in due course be able to plead not guilty at court. The prosecution will present evidence of his guilt (photos, operator statements, etc), and in his defence he will say what?
If (when?) found guilty he will get the same 3 points, but the cost will be nearer £1,000. Much more if he employs a lawyer, or expert witnesses are needed.