Well I worked it out where I had heard it before - it was fairly obscure, but it was interesting to research and brought back some memories.
For those interested, I recognised the melody from the Dragons Megademo released on the Amiga demoscene in 1990. Part of this production (called the "Unlimited Bobs Demo") featured a tune called Spaceship505 by a dutch Amiga musician named Zzzax, which uses the melody from the Droids original.
Here is some info on the song: http://www.scenemusic.net/demovibes/song/252/
And here is the megademo playing in an emulator, the unlimited bobs section starts around 27': http://www.youtube.com/watch?v=cQQagCMFJLo