The lad (Peter Auty) who sang Walking in the Air (which is actually flying but that's another discussion) in the short cartoon film wasn't the same lad who sang when the song was released as a single after the movie was released. Aled Jones got to number 5 in 1985 with the song. So the first time the song was covered and released as a single it was a hit.
The Snowman was first shown on TV when I was 2 and I still watch it at least once every Christmas.