That picture is almost identical to what I have built :)

i have designed a carriage for the x axis on the gantry and will start machining it as soon as the aluminium arrives. It rides directly in the gantry beam, pretty much like the one in the eBay listing you added, but mine is made out of aluminium slab, same sort of bearing layout though.

hopefully have it made by Monday as I'm still finishing the gantry trucks and motor mount.