If the screen was completely white, or completely black, or only had some arrangement of lines through it, I would suspect a damaged flex cable through the hinge. Since you mentioned "a blodge of black", I'm assuming you mean there is no real geometry to this figure. Broken LCD's normally will still light up but will have black areas near the point where it was broken (from excessive pressure, etc.) and the vertical/horizontal lines tie in with that as well. It sounds to me like you are in the market for a new LCD my friend. It is unlikely that it is a motherboard or connection issue. I hope this helps, cheers!