The problem seems to have been with the settings in the displacement exporter in Z-Brush. I was reading about the differenc between 16 and 32 bit maps, and where id tried the 16 bit type first of all, when I then switched to 32bit, the 16 bit type was still checked to on. So I was creating two maps at once which I guess were messing each other up.

As for the grid like look of the map above. A guy on zcentral said thats what it should look like too. I know that when you create uv maps in zbrush they do have that broken up tiled look, but actually the displacement map Ive had success with looks a lot more like what it represents. In the tutorial video I watched aswell, the displacemnet map for a character, when opened in photoshop, looks recognisably character like, you can see the eyes mouth nose etc. I wanted to post up a picture of what my displacement map looked like, but opening Tiff's in photoshop, i cant save out as a jpeg. But this next picture is the result I got in Maya, and the map for it looked like a load of squiggly lines with arrow heads, not the grid type thing above???