everyone raves about Norfolk flint and apparently, it is the hardest flint in the world rating 8 Moh's. I do have a soft spot for the English flint but as you note mate our Aussie flint compares well against it.
Thinking about this test though, the results can be skewed a bit depending on who's doing the testing (how hard they do the striking, and thus prematurely degrading the edge, the experience of the tester, again the more experience the tester the better they can make the edge last) and the type of edge you start with, I started with a fairly robust edge and it lasted quite well but if you started with a sharp but fragile edge (a thin one) it will chip and degrade quicker.