Sorry for double post but:
It gets better: The damn thing now works! I had to test the psu fan, which needs the pc to be rigged up to it. I wasn't sure if it was spinning.
The only thing I did was connect the power to the MoBo and used a different CPU power wire.
And now it works... Solved I guess till it dies again..
EXTRA info the only thing I can't understand is why has this happened?