This gets me on to problem #2 - I can't get any of the overclocking tools - AMD GPU tool, MSI afterburner, ATItool to work with my current crossfire config. I should have resistors turning up for dummy plugs tommorow, hopefully that will resolve that.
Removing the crossfire bridge and using dummy plugs would be better, as then you can clock them individually using for example MSI Afterburner. That's how I plan to run my dual 5870 setup.