moving the ground (origin of axes)

[micheus]

JulesJH, welcome to our community.

There is no way to change the ground location - its default place is in the middle of the geometry window (always you reset [R] the camera location).
So, what amfitrione has suggested would be the best option. In this case, I suggest you to select all objects and Move->Y by the necessary amount of Wings3d units (WU), but use the constraint key SHIFT together then it will "jump" by 1WU each step. That will make easy you put your object back to the original position when exporting it back to .OBJ.

Some tips:
a) Just in case you need edit around it, I suggest you to try the View->Highlight Aim [A] option. Just select any element in the scene or put
the mouse over one element (that will get highlighted) and hit 'A'.
This way you will temporary change the centre of rotation for the camera. It returns to default after you reset the camera [R];

b) in case you uses to use any other 3D application, Wings3d allow you to choose between some camera mode used by them (Maya, 3dmax, Blender, Sketchup, ...). Check the Preferences->Camera;

c) and the most important: pay attention to the information line - it's where Wings3d uses to talk to us.