@temkem Tried your suggestion of adding disable-background-networking to my desktop shortcut and so far Opera hasn't nagged me to update. Not too happy about losing the ability to update extensions, but it's a small price to pay to stop Opera's harrassing me to update.
@leocg I had already deleted all files named auto update. I have been doing that for a while now. I never rename them, just delete them. Also I could find no temp folders for Opera.