What it does do however is allow you to fly VFR on top in France, a privilege conferred by the standard French PPL.
Not quite.
What the IMCR does is it removes the UK CAA's requirement to be
in sight of surface when VFR.
This removal is not restricted territorially i.e. it is valid worldwide - not just in France.
Nearly all countries do
not have the UK requirement to be in sight of the surface for VFR.