chopping the corners off a block

[micheus]

I've cut the faces so that the entire block is divided into small cubes, what I want to do is remove the top left and top right of those cubes.

If you want to produce to holes that is the command you should look for [Hole]. In this case, you will see the back faces through the hole - not internal faces. If you need that, then you may need to use Intrude which you can define a thickness for the mesh.

Wings3D works with closed meshes, so you will not be able to remove the faces with any other way.

If I take the 4 faces and 'extrude' inwards it looks like the cube has disappeared

yes, that will not work.

If I start with the block short, divide up the top face and extrude the middle piece upwards I get the 'head and shoulders' I want

Do a test with Inset [LMB]. Moving the mouse you will "scale" the new face and keeping pressed the [LMB] and dragging the mouse you will bump the face.