how do I stop the auto updates for sites which I know …etc
Following code at least should prevent auto updating:(add in wp-config.php)
define( 'AUTOMATIC_UPDATER_DISABLED', true );
Here you find an (imho) handy explanation about the how to handle in which cases:
Chip Bennets “readers digest”
Another nice informative page is following: The definitive guide to disabling auto updates
And ofcourse some Codex information about the issue.