Installed Nokia PC Suite.
Exported all the messages from the old phone as a .csv file.
Loaded the file into Excel, deleted all columns apart from the message body one, and deleted a few rows of rubbish.
Copied the modified file to my O2 XDA.
Using Basic4ppc wrote a small program that reads the .csv file a line at a time and sends the text via SMS to her new phone.
Simples. :sign0060: