I have already connected the ATX12V1 power cable I believe correctly - this is the one that goes into the CPU slot on the back of the PSU correct?
I tried removing everything except the CPU and 1 stick of ram from the board to no avail and then attempted the CMOS trick - no joy anywhere.
This is how the board and back of the PSU look:


Do you have a power switch connected to the board if this rig is not in a computer case? You said you turn on the PSU and nothing happens but lights come on. I am guessing you are doing this with the switch on the back of the PSU? You still need to somehow short the 2 power switch pins on the motherboard by either using something metal to connect the 2 for a second or with a power switch.
This could well be the problem - I dont have an on/off switch - just the PSU switch. Anyone with this board know where the power switch pins are located? What do you guys use for this purpose?
Any other input appreciated. Thanks guys for all of your suggestions.