From what I understand you're still in sight of the surface while above no more that 4/8 cloud.
I thought the French are still allowed to do VFR on top so their licenses must read differently (i.e. no "in sight of the surface" phrase).
Krallu - what does your license say in the privilages or limtations section? Or perhaps you could check out the Swedish Avaiation Authority website?
Why we don't allow it here - don't really know. But my thinking is it's a really bad idea anyway without a IR or IMC. What if the cloud base thickens and you cannot find a way through? Or you return to a position where is was okay but now isn't? You're forced into IMC, breaking the privs of the licesnse.
And in a country the size of the UK with so much CAS you need to be really careful when ontop to avoid busting it, probably not such a problem in the US or France, hence why they allow it.
And before someone makes the argument that your less likely to bust CAS on radio nav, think about the amount of training the average PPL gets on radio nav!
Get an IMC or IR and be safe! (I have neither and wouldn't DREAM of flying on top! Starting my IMC rating this winter though....)