There appears to be a number of ways to challenge these things, and for some people (I know 1 and possibly soon 2) ignoring NiPs has been done and nothing more has been said or done.
Other action includes beating them at their game, ie playing on technicalities (they want cash out of you for a technical offence). E.G If you are the registered keeper then the NiP must be served with 14 days (allowing a day or two for delivery) and it must be sent 1st class. Ensuring that the temporary limit has actually been approved and the signing was correct can also yield dividends.
You mention the “Hamilton” defence In which case you need to show that you have been diligent in trying to ascertain the driver at the time, and this will usually mean a visit to court to see if the Magistrate believes you or not – the more questions you ask the SCP, times etc, “anything they can provide to help you identify…” etc will help, as will providing a list of possible drivers. However admiting the alleged offence on a public web forum prior to going to court may not help, and in fact could cause some further problems.
The PACE Letter also seems popular and it seems used to good effect, but as has been said get yourself over to Pepipoo and have a good read. If you do get a a NiP then post on there in the manner requested.
Either way if it goes to court and you get nervous then plead guilty, ok the fine will be more but at least you can sleep easy that night knowing that you have not contributed funds to the parasites that are feeding off the increasingly poor road safety they love (IMO).
Cheers
Paul