SpringHeeledJack,
Yup, as of 10.7.x, it can now pull and notify.... rather than just notify and pull on demand.
If you go to your Software Updates System Preferences, you will see an appropriately labeled checkbox (only two to choose from, so I'll leave which one as an exercise to the reader ...
)
Bear in mind that it only downloads and doesn't install.... so you're not actually risking anything by letting it do that