Colin, IMF Updates will be availalbe through the Microsoft Update service, it is now one-stop updating for all Microsoft products. Actually, preferred method of installation is manual. After all, AU is not 100% true auto-update as with this option you will get a bunch of other updaets that you might not even care about. If you opted-in for AU, you still need to select what updates you want to install (unless you want it all -:).
Manual mode - you need to go to the MU website, and select 'Custom' button as described in my blog. The link to the website is also in the blog, please give it a try! The detection logic will offer an IMF Updates package to you and all you need to do is install it! Let me know if you have more questions.