Jau
Assuming you're talking about the UK (you don't actually specify) then everything you say about VFR/IFR/VMC/IMC sounds correct to me, with a couple of exceptions
You say that "IFR... MUST be used in... class A airspace." This is not correct. VFR is not allowed in Class A airspace, but SVFR is - and it's quite normal to use SVFR to transit both the London and the Channel Islands CTRs.
As for VFR above clouds, you certainly can fly above a scattered or broken layer, as long as you are within sight of the surface - but you must remain 1000' vertically (either above or below) the clouds.
Flight out of sight of the surface I'm not certain on, but as far as I know there is nothing within the Visual Flight Rules that prevents this. The thing which prevents it is a restriction on your license if you don't have an IR or IMC Rating. What this means is that an IR or IMC holder can fly, IFR, through an overcast layer and on to the top of it. Then, once on top, he can declare himself to be VFR again, and thus not have to follow the quadrant rules. I doubt that this has any real use, though, and I'm not 100% sure that I've got it right anyway.
Outside the UK, the situation is very different - many countries don't allow IFR flight without an IR, for example.
FFF
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