Englishal
Sorry to contradict, but your understanding of French airspace is dangerously wrong.
You are correct to say that an ICAO IR holder may exercise the rights to fly in IMC outside controlled airspace. Where you go wrong is in assuming that this applies in France.
In France, nobody may fly in conditions less than VMC unless they are under IFR (surprise surprise). To be IFR in France requires the commander of an aircraft to hold a valid instrument rating and to have filed an IFR flight plan. No problem if you have an FAA IR and you are in an N-reg aircraft.
You are half right that the French take the view that if something is legal in the pilot's home country, then it is OK in France too. This only applies if the proposed activity is also legal in France.
Flying under VFR above a solid cloud layer is legal in France. Therefore, the French take the view that if it is also legal for you at home, then it is legal for you to do it in France. By contrast, the whole concept of flying in cloud, without an IFR flight plan, and without a current and
valid IR is totally illegal in France, and will not be allowed for you, just because you can do it under the ANO in British airspace.
If you wish to
validate and FAA IR for IFR flight in France, you must be a non-EU resident, and the validation is a temporary one.
If you want to fly in cloud in France, there is no way that this can currently be achieved without a valid or validated IR.
Trust me.
Charlie.