When going down the road of describing pilots who legally fly a single engine aircraft above an overcast as "unsafe" on the basis that any engine failure will require flight in IMC, please remember that you are at the same time describing pilots who fly single engine cross water as "dangerous" because while an engine failure in a microlight above an overcast with 1500ft base may not be nice, it is entirely possible to acheive a safe landing (with an experienced pilot).......................the same can not be said about ditching mid channel (with the same pilot).
Flying is all about balancing risks and it is impossible to have any form of flight totally without risk.
2 Pilots - 1 flies within sight of the surface and gropes round at minimum levels in 3k visibility...........the other climbes above the haze layer to 100k vis and in order to remain there will from time to time be out of sight of the surface while crossing some cloud. Both are taking on risk.......but perhaps number 2 has the least risk of collision, CFIT etc.
As Genghis says, don't mix up "legal", and "safe".............60mph on a back road is legal......may not be very safe though!
Of course when dealing with the legal reuirements, a non-IR holder and non-IMC holder can fly above an overcast legally provided that somewhere in the distance there is the top of a hill sticking up through it.
Personally, the problems in understanding the UK system stem from the fact that airspace requirements for VFR and Licensing requirements for VFR are different.
Why can't the CAA simply say that regardless of pilot qualification all VFR flight must be in sight of the surface.............or even better, comply with the ICAO requirements and simply say that VFR flights must comply with VMC minima.
But of course if the CAA was to let PPLs fly VFR out of sight of the surface there would be a fall off in the uptake of the IMC course and the training establishment would not like that.
Regards,
DFC