I must admit I didnt know ICAO airport designators were not permitted officially, so this was interesting to read. Does this illustrate the differences between the overall understanding a PPL compared to a PPL/IR who wil be given much more (and more legitimate) forms of filing flight plans?
No; the
JAA IR theory is completely useless for flying anywhere. They teach you ways of developing IFR routings which ceased working at least 15 years ago.
IFR flight plans (ones wholly within Europe) are sent to just two fixed Eurocontrol addresses, and the computer then re-transmits the FP to all IFR controller stations along the route, some time before the filed EOBT (typ. 10hrs or so; each country can choose).
You don't specify EETs to FIRs or anything like that, on IFR FPs. Not in Europe, anyway. The way the system works, countries are immaterial.
As I said,
VFR flight plans are rarely looked at, never mind checked for validity. But the scenario where a VFR pilot might get stuck is if he is getting a notam briefing for a route. The
NATS website mostly used in the UK enforces the correct ICAO flight plan format and would object to a route containing ICAO airport designators. Which leads to the Q: how do you get notams? I suppose a site
like this would not enforce anything.