Okay Ty, now you're trying to confuse me! There is no wire coming out the middle. The unit comes with two black wires attached to the left and the right - and of course the green ground wire.
I'm going to try and settle the issue tomorrow by attaching a standard switch and see if that makes a difference. If everything works fine then it has to be an issue with the dimmers. If not then I have no other option left but to put a gun to my head and pull the trigger!