Seg,
The dishes are offset fed (the lnb is not held in the center of the dish) - in this case, the dish is offset by about 20 degrees - in order to have the dish pointing horizontal, it either needs to face down 20 degrees or be turned upside down and point up 20 degrees.

I think sky dishes are the same, either way, they have a guide on the back of them which is pretty reliable if the mount pipe is level.

I have a sky dish up for grabs if you want it....Its missing the 2 u bolts, but apart from that complete - you could try either a biquad or can feed on it.

Cheers
-John

Edit: I belive the waveguide gets the signal as far around as the harbour bridge so you should be well within the 17 or 18db zone where you are.