Hey Andrew,
I think I'm chasing my tail here and sorry about the frustration levels.
The "multiple pages" under "Page Setup" is set to "Normal", not "Mirror Margins" so I'm assuming that means Mirror Margins is off.
Everywhere I can justify, whether it be in the paragraphs style or page set up is set to justified so I'm assuming that is fully justified.
I'm happy to do this via email if it makes things easier but I simply cannot see anywhere where the document is not justified except where it shouldn't be such as headings.
Cheers.