Stick at it Zany Mouse, its worth it. Nothing terrible happens if it all goes wrong. I've seen a well know and paid shanty singer twice stop a song which he forgot and start another song in a wrong key all during one set - so what! We all do it sometimes and in my case many times!   When the "so what factor" gets into your brain, some (but only some!) of the nerves disappear and the quality of your singing improves!

"Dancing and singing, bell ringing ...!"
Alan