@ MikeJ,

I know that you have already put a lot of work into the new UVs, and I think everyone would understand and accept if you don't want to do any more work on them, as they already work fine on the high res figure. And I think we all appreciate very much having to new UVs. But I think you are not understanding what odf is saying, so I will try to say it again in my own words.

I think this is what odf is saying. For every 4 polygons in the high res mesh, there is only one polygon in the low res mesh. In order for the UVs to work on the low res mesh, the UV seams need to fall on the edges on the low res polygons, but some of them fall halfway between the edges, making them half a polygon out on the low res version.

In the above image, the green lines represent the texture template of the low res figure. The red lines represent the texture template of the high res figure. Some of the seams in your UV map fall on the red lines, but to work on the low res figure they need to fall on the green lines. By the very nature of the meshes, the seams can never be out by more than half a polygon, but that half polygon distance is enough to stop the UVs working on the low res figure.

To make the UVs work on the low res figure the most you would have to shift any seam would be one high res polygon (=1/2 polygon low res).