Well, 2D, in my case the 'myth' was perpetuated by non other than the CAA. Guess it's time for a call.....
I wrote to the CAA some years ago to clarify the point, and indeed they said that there was no "day VFR" restriction. They kindly incuded the relavent points of the ANO. They also said I could use my FAA ratings in a G reg aeroplane (e.g. ME rating) and that the IR could be used outside CAS without formality. While only valid outside CAS, it does remove the insight of the surface restriction currently imposed on JAA PPL holders. As it is, they also gave me an IMC rating to attach to my JAA PPL without sitting any exams, and without taking a flight test (for a fee).
I also wrote to the French authorities and asked if I could fly a G reg aeroplane on my FAA ticket into French airspace. They said that as long as the CAA allowed me to fly the G reg, then they would as well.