The Channel Islands are not part of the UK. As far as I am aware the only link they have with the UK is that like Canada and Australia, they have the same person as Head of State(s). The teritories and their teritorial waters and airspace belong to the State of Jersey and the State of Guernsey (not France and not the UK). They are also not part of the EU.
For ATS regional reasons, the Channel Islands lie within the Brest FIR. As independent States, the CI decide what and who can fly in their airspace and what regulations pertain including what class of Airspace. These details are published in the French AIP and by agreement the UK AIP.
The Manager at Guernsey was perfectly correct to say that holding an IMC rating removes the requirement for 10K visibility when on a special VFR clearance. However, that applies world wide provided local regulations are not more restrictive.
When it comes to flying a UK aircraft abroad, there are two issues.
1. The aircraft must have a valid and appropriate ICAO C of A. If it only has a permit to fly then prior permission of the non-UK state is required. Some countries within Europe have given automatic right of access to certain UK permit to fly aircraft and the UK recriprocates.
2. The pilot must hold a valid ICAO standard licence. National licenses and Ratings may be accepted if an application is made (has anyone applied to visit France on an NPPL in a C172?) and approved. Microlight pilots are not licensed under JAA or ICAO. Thus only National Licenses exist for Microlight Pilots. For that reason, many European countries accept National Microlight Pilots from the UK without prior permission and the UK recriprocates.
The holder of a valid NPPL SSEA rating can fly Microlight aircraft provided differences training has been completed and signed off by an instructor. This means that there is no need for a pilot who keeps a valid SSEA rating to obtain a microlight rating to fly microlights.
Overall, the biggest difficulty that other countries have with the NPPL is the medical standard. If you can drive a private car you are fit to fly solo or with another qualified pilot as the passenger. How many private cars are driven by people with poor eyesight? For these countries, to use an NPPL even with a microlight rating requires the pilot to at least hold an ICAO standard medical (JAA class 2).
So I expect that it is easy to apply for an obtain permission to fly a UK C172 round Europe if not the world on an NPPL provided one has a JAA Class 2 medical!
Regards,
DFC