I'm not at home so don't have access to a 360 box at the moment so this may be slightly off.
But, for filtering existing recordings it's Saved > All Recordings and then there is a drop down option where you can pick (I think) 'Recorded shows on this box' or 'Planned Recordings on this box'
When you set a Series Link to record in the Advanced Settings there should also be an option as to which box it records on.
There is also place in the Settings I think where you can pick the 'default' box.
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I work for Virgin Media - but all opinions posted here are my own