Hi Laurence!
It sounds like this could be many different things. It was good to check the LCD cable connection! That is a good starting place. I would check all of the display connectors (any digitizer and LCD cable connectors). If these all seem to be seating well, go ahead and get the magnifying glass to see if all of the pins on the connectors seem to be intact. If one of the pins on the connectors( the little gold lines) seem out of whack, then that could be causing the problem (and is unfortunately a pretty tough fix if you aren't familiar with soldering techniques). If all the connectors seem like they are working, I suspect the drop could have damaged the LCD itself. I imagine you do not have access to an extra LCD, but if you can swap the LCD's to test a different one, you will get an answer. It is also possible that the board was damaged, but I suspect the LCD. You can probably track down a replacement LCD! Let us know what new things you find on your hunt.
Good luck!