2011 R56 S major squealing
 

See the video to the end. Has anyone encountered this?

You tube video:
I know that the valve cover is leaking but the latter noise is troubling.

2011 R56 hatchback with 68K miles.

I'm wondering if that is a hissing sound we hear. If your valve cover is leaking, it could be allowing some sort of vacuum leak. What I recommend doing is a smoke test of the vehicle. If there is a vacuum leak somewhere it will pinpoint exactly where it's coming from. A local MINI independent shop can do this for you if you do not have a smoke tester. As you can see a smoke tester is not cheap: Pelican Parts - Redline Detection Smoke Pro Total Tech. Let me know what you find.