I just finished UV mapping a large object that was split into many parts, some parts were new and made in Blender, but the original object was built in another package, which uses a different default UV map name, so that when I joined the new objects to it, I ended up with multiple UV maps on the same object when I just wanted one.
Although I fixed my problem by undoing the merge and renaming the UV maps to all be the same before merging again, I would like to know if there is a correct way to copy UV data between different maps on the same object, or of merging multiple UV maps into one.