The problem with PNR (prior notice required) is that unless you obtain a positive acknowledgement, you can't prove they received the "notice" and if the person at the said airport is the d1ckhead which so many airports (notably certain ones somewhat south of the UK) are staffed with, they could just turn you away when you are on final. I've had that happen. You might have sent several faxes but if....
So PNR is de facto same as PPR.
This is why PNR/PPR is such a problem in aviation.
It's OK for the "advanced Goodwood to Bembridge UK PPL over-water journey" because it really is just a phone call to Bembridge who will not cause any trouble whatsoever.
But extend the principle to airports where they can't (or more likely won't) speak English despite being international/Customs, or the published numbers are duff, and you can see the problem.
With the application of time and money you can make flying pretty smooth. You can get yourself a nice plane ("just money"), get yourself an IR ("just more time and more money"), but no matter what you do you are still up against the 4ft tall d1ckhead bloke who wants to feel important, and nothing makes him feel more important than turning away somebody who is 30 seconds away from landing after flying there 500 miles. Or perhaps he just doesn't like N-XXXX because he doesn't approve of American foreign policy
And there is no real solution to this.
Airlines etc work this by having staff who make the right phone calls, send the right AFTN messages, and generally have good contacts (including people in the "3rd world" country's aviation ministry) to make sure things happen and the fuel turns up etc.
Lower down the scale, one solution is to always use the local handling agent. His generous fee sometimes lubricates the airport manager so again things happen (whatever the notam says).
GA pilots tend to be stingy and understandably cannot see why they should pay £200 handling (which they don't need) when they can land there for £20. This is where the fun start
I am currently trying AFPEx and its ability to send AFTN messages, for this purpose. It seems to work OK.
But the other week I was going to take my girlfriend for a day to N France, and most of the several possible airports were Customs-PNR, and none of them answered the phone. I could not be bothered to go there.