New version

Posted an updated version of my prototype today with mouse scrolling which you can get here. Just hold down left mouse button and move it to scroll. Make sure you press D first to see the draw list fill up and empty out as objects come into view. Pretty neat. There's a read me with all the controls inside. Remember this is only a test program so the controls are not particularly well selected. Here's a screenshot with some objects stacked on top of each other and still being drawn in the correct order, which is something I'll go into with my next post. BTW, the blue cube and the two chests have incorrect dimensions so may result in depth sorting issues. This is not a code bug, but a bug in the object which I'll get round to.
Run IsoTest.Exe

Controls

Hold left mouse button and move mouse to scroll map

Up = Move object north
Down = Move object south

Left = Move object east
Right = Move object west

Q = Move object up
A = Move object down
There is a known bug sometimes when an object is on top of another object which causes the objects to flicker.
It is known, and I know why it's happening so I fix it when I get round to it.

M = Select next object

O = Change object type (If object is changed and ends up becoming intersected with another object as a result
(i.e object suddenly gets bigger and is "inside" another object) the object will not move until it is no longer
inside the other object(i.e is changed to a smaller object to when it go stuck).
Best used when object is away from surrounding objects.

1 = Increase width of object
2 = Decrease width of object

3 = Increase height of object
4 = Decrease height of object

5 = Increase depth of object
6 = Decrease depth of object

7 = Increase anchor X position
8 = Decrease anchor X position
Anchor is the drawing offset of the object's bitmap, it should be the pixel that corresponds to the rear bottom left
corner of the object. Best not to touch this as it will bugger up the drawing position of the object.

9 = Increase anchor Y position
0 = Decrease anchor Y position

D = Enable debug mode
This shows the draw order of all objects(Constanly changing)

All graphics are mine so please don't steal my poor programmer art.