Is there a way to copy UVs between maps on the same object, or merge maps into one? 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.
You can copy UV maps from one object to another (provided their vertex count and index match) by selecting one object, then shift+select the second.

I press spacebar - type in "UV" and select "Transfer UV Maps".

I'm not sure but I think the order is copy from object 1 to active object. You may have to experiment to find out the correct selection order (use UNDO). It will copy to the currently selected UV map in the "Object data" tab.