Check the Power Steering Pressure Switch, mine leaked from there a couple of times. Not too sure what causes it to fail, but mine was leaking
through the switch assembly and out the electrical connector.
To get to it, I believe it's a 14mm, find a sacrificial spanner that you can cut short and grind a bit of the thickness off it so that the 'prongs' of the spanner come to a sharp point.
There's not much clearance to get a spanner in there, so it's easier to just cut the spanner short.
There's a diagram here which shows where to find it.
http://fordforums.com.au/wsmpub/augx/Part%203-3.html