The alternate "thing" version gained steam in 1983 when British Heavy Metal mavens Judas Priest charted with You've Got Another Thing Comin' off Screaming for Vengeance. In the song's chorus, lead singer Rob Halford clearly says it as You've got another thing comin'
Perhaps the phrase is different in Sheffield, or perhaps the lads are rockers but not rocket scientists. Nonetheless, this song helped entrench "thing" in the popular psyche of the mid-80s.
Incidentally, may favourite part of the track comes near the very end, during the fade. Rob Halford is repeating the chorus during the fade out, and you can clearly hear him wearily toss "it's a long song" into the lyrics as the track winds up.