yeti,

thanks. But I've not explained myself properly it seems.

I understand how to lay out UV's, the various mapping options etc. I also know how to create new topology for a mesh and how to transfer the texture from one to the other.

you're correct - it's does create a 3D mesh from photos, it also used the photos to texture the mesh. But when it first comes to you, the textures and uv's are all over the place. There's nothing you can do about it, that's just the way the photos are interpreted. This particular mesh is false teeth, but the recap system has to map the whole surroundings too, to properly construct the scene, so you get a load of extraneous geometry which you need to pare down. the mesh is heavily tessellated too.

I'd be ok if there was just one set of uv's for the mesh, but there's two and I don't understand how to deal with them.

hopefully this makes a little more sense