Thanks bcd
I followed your lead and went back to the basic structures, no cutouts etc and had indifferent results, as well as going back to previous version.
There seemed to be no continuity of which piece was corrupt (or miss drawn...)
However with a little investigation & re design within Subdivision I made it a whole piece, then added the cutouts, chamfer etc which maybe a better workflow...
I will pass on to my 3D printer friends if they can make it either sold or honeycomb.
Although it would be really useful to know how to make a true solid in VW.
Thanks again.