RE: Pepakura
You can use the Export UV Info as Wavefront (OBJ) file.
Then when you import back to Meta, make sure the checkbox, "invert x axis" is checked. (Otherwise, the UV maps will be flipped horizontally.. weird.)
Once the import is complete, you'll get one single object. If your model was previously comprised of multiple objects, and you want to keep it that way, you'll need to break apart the model to individual objects again. It should not be a big problem though. You'll just need to use the "select joined faces" to single out each component, then cut + paste to new object.
There is one problem though. The UV Map is technically "correct".
However, the height vs. width ratio is off. You'll need to do some resizing to get the ratios correct.