Apologies Nick, the post above was actually meant as a reply to PaulS. I should have quoted his post but I was running out of character space so I just didn't bother in the end.
I do actually have an I2C LCD but I bought the serial LCD specifically because it makes it easier to use with this code (which I myself didn't write by the way, which I should have said).
I'll wait until PaulS gets a chance to reply but if I don't have any luck then I will consider doing exactly what you suggest - reposting it with a better title. I am grateful for your useful input though.