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I've been trying for years to identify a full-length SF anime film which was shown on British TV two or three times in quick succession in the late 1980s or 1990s.
I'm 90% sure it was Japanese, although the figures had normal human proportions and faces, with no cuteness or big eyes. The style, as I remember it, used very clean hard-edged lines and colours, with no scribbled lines and not much shading.
The story centred around a little boy, maybe eight years old, who had ended up stranded on his own on a planet where all the "creatures" were kind-of plants, but behaved to some extent as if they were animals. I remember a scene of him being carried across a lake by a giant water-lily which behaved like a semi-sentient boat.
Meanwhile, a large cast of characters were flying a starship to rescue this boy, but there was a lot of personal and political struggle on board. One of the characters iirc was an aristocrat with long white hair, a bit like the film version of Lucius Malfoy. One of the characters - possibly the aristocrat - turned out to be plotting against the others.
At the end, you learn that there is a time-slip involved, and that the little boy on the planet is the childhood self of one of the adult characters on the ship.