Well, I had to pull it off as the bolt holes didn't quite line up properly and I ended up snapping the bottom left plastic mounting tab off.
Anyways, I've glued it up and did some more drilling to try and get all the holes lined up.
Below are some pics of my mounting bracket. It started life as 200x60x40 (2mm thick) one of these...
http://www.rcr.com.au/metalmate/carinya-brackets/make-a-bracket/angles
Which I bought from Bunnings for around $6.
It's too hard to describe on here how I cut it so hopefully the following pictures illustrate it well enough.
The bits I cut out of the bracket I bolted to the back of the bracket to reinforce it. It almost perfectly lines up with the 4 mounting holes under the headlight. All that's needed is to elongate the holes in the bracket so that all 4 line up properly.
Make sure they do line up properly otherwise you'll end up snapping off one of the bottom plastic mounting tabs.