Tannywheeler, your 'mystery Scot' is indeed Brian McNeill, as John B suggests. Reading the thread title I immediately thought of his Sell your labour not your soul. It's easy and fun to sing, available on 'If It Wisnae for the Union - Scottish Trades Union Congress Centenary Album' (1996). Brian says he wrote the song specially for that album, but he often does it in concert and, by the sound of it, gets even union-haters to sing along.