HELP!

There is an old animated movie I watched when I was very young (during the Betamax days) that I am desperate to find know. I think it may be a late 70's or early 80's film.

All I remember is a very kid, (I think a blond boy) stranded or alone in a jungle/forest which I think on an alien planet. I think he had a robot or something with him as a companion but am not sure. I only remember that it was a sad ending with a haunting choir song (or hum) as it ended.

I don't think it was Japanese or at least typical 80's anime style but I could be wrong.

A 20 year old question in the waiting...

One Million-Year Trip: Bandar Book / Le Prince du Soleil

Or maybe Time Masters

Thanks for the responses, have checked but unfortunately neither are it. :( Any other ideas?