Got myself the official Nokia case CC 3015(black) for only £8.because the store overstocked.
Although the design might not be everybody's cup of tea,it is,as far as I know the only case that will let you put your phone upside down on a surface.
The four corners are protruding and therefore the screen can never touch the surface its put down on.
Needless to say I don't use a screen protector and so far not a scratch or mark on my screen.

http://europe.nokia.com/find-product...5-for-nokia-n9