A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Hello Simon,
To disable the AutoSave feature in your Office 365 is ideal. You may please raise this as a feedback ticket in Office365 UserVoice.
Meanwhile, we would like to set your expectation that in Office 365 ProPlus, you can disable it by adding registry items. You may check this link that talks about How to disable AutoSave in Office 365 ProPlus.
Note: You can turn AutoSave Off for a file, and the program will remember to keep it off every time you reopen that file. This method will require discipline. If you switch it back On for a file, it will remember to keep in on for that file. See more here.
Best regards.