I have turned auto update off, but it still updates to the next version. How do I stop this please?
Which Auto Update are you talking about? AFAIK LibreOffice can perform an automatic download (!!!) but cannot initiate an automatic install/update. So the question is unclear and seems to be not related to LibreOffice but some other procedure on your system (Have you got some third party tool, which keeps your software up to date, like Avast Software Updater, Avira Software Updater, and many others).
Since you did not even tell us your operating system, no additional hints can be given.