I am also curious as to why nine ships of the line were there as well. This term was only used for wooden sailing battleships. I'm pretty sure the RN wasn't still using them as convoy escorts.

I'm sure that it is possible to write a good song without employing bad history. History nerds (like me) will just get put off. Don't get me going about 'the band played Waltzing Matilda'!

Coal was an important cargo. There were many coal-burning ships serving the country - in fact they were still being built.