Thankyou all for your input, I have found this discussion very usefull.
As for navigating without sight of the surface, I was taught VOR use (tracking and triangulation) during my PPL.
I think the real use of the "within sight of surface" rule is that as a "plain" PPL you need to be able to see the ground to get back to it. You haven't learn't instrument approach procedures yet. If you fly off across scattered cloud which becomes broken and then over(under)cast; how do you get back down below when you want to? Maybe the weatherman is wrong and its not "scattered" at the destination aerodrome, or anywhere else within range...