I ended up shooting earlier in the afternoon so I had a bit more light to work with and took along a small set of flood lights. The flood lights didn't appear to do much but there was a slight improvement in light. We also ended up shining the car headlights onto the digger to try and brighten it up further. Again not sure it did a lot.
I shot the subject standing a fair way from the digger so I could get him filling a more of the frame. I positioned a softbox to my right and set the camera on a timer so I could run around to the left and hold a reflector to bounce some light onto the subjects right hand side. I shot at ISO400 and a shutter speed of 1/10sec just to capture enough light in the environment.
The shot came out ok but not quite what I wanted. With some photoshopping it was acceptable. With no time to reshoot it would have to do :)