Valmai asked:

Were Alvin Stardust and Melanie ever in the charts at the same time?

That would be a yes! The chart of 2nd March 1974 saw Alvin Stardust at No. 2 with 'Jealous Mind' and Melanie at No. 37 with 'Will You Still Love Me Tomorrow'

Given that 1974 was the year that Mike Yates recorded the song from Packie, I reckon your on to something, Valmai.