Went through again, clearing all similar names.
On checking the vertex and facet point, the ,obj file that emerges from the3D modeller has a v list and an f list, presumably why it is visible when first imported into Poser.

When I re export it from Poser as an .obj file to UVMapper it has no f list, which is what UVM reports.  
When I save the visible breeches as a prop to the library, the .pp2 file also has no f list , which presumably is why it doesn't show when I try to bring it back into Poser.

Conclusion; when Poser has to work with this file it fails to copy the facet list.  Why?

1. Is it a Service Release problem? PhilC on the UV forum mentioned a bug fixed by SR 2- my version number is v7.0.2.127, am I up to date?
2. Is it to do with the original export options?-Weld body part seams and Include body part names in polygon groups checked, is something missing?