Will look at that later today - you are of course right that VGA (RGBHV) will send High Def signals - only reason I didn't put it in was that I've only ever seen VGA used in computer applications - but I supopose you can send HD from a computer to HD screen so valid point.
The point about luminance separately is that there are basically 4 components to video (if you exclude syncing - which I don't really understand if I'm honest) - and YPbPr component separates them out into their 4 components, the 3rd colour being inferred from the other 2 colours.
Thanks for the constructive criticism though, will edit the post later
