I also commented out the referenced to #APEX_CSS# in the header so it would use my uploaded copy and not be overridden.
I took these lines out, uploaded again and it was fine and my change was visible, meaning that the #WORKSPACE_IMAGES#apex.min_copy.css was being read correctly. I can also browse the location of these files on the xdb database using a browser connected a system and I can see the files where i expect them to be.What I cannot understand is how other references to images in this css file such as
background-image : url(../ws/report_bg.gif);
do not cause an issue but the one mentioned earlier(/ws) does
background : url(../apex/builder/dev-bar.png) 0 0 repeat-x transparent; background-image : url(../htmldb/builder/builder_find_bg.png);