Dave, why not just use the Snap to objects control.
Highlight all the objects. Shift Click the leftmost one and drag the grouped objects until they touch.
Shift click the next left object and repeat until all are touching.
You can hold down the Ctrl key to ensure the objects stay in horizontal position while you drag them.

To set positive or negative spacing at this point you hold down the Alt key and use the left and right keyboard cursor arrows: one click is one pixel at 100% Zoom.

Acorn