Incidentally you can use the airways in France as a PPL as long as you fly at quadrantal levels plus 500 ft
You no doubt meant semi-circular levels in France, not quadrantals.
IFR in Controlled Airspace is simpler, safer and considerably less stressful than the alternative.
All the IR pilots I know say the same, and it seems one of the big attractions of doing the rating if one needs to do that sort of flight.