Owners of the Foxsat-hdr may be aware of the thread here detailing the various multiple recording and viewing capabilities using a single or dual cable installation.
While the information there is generally relevant to the HDR-1000/1010s there are a few differences.
Firstly for single cable use there is no need for an external coax loop cable. Single cable users report that an automatic internal link is provided.
The Foxsat-hdr only provides third channel viewing with time shifting capability in the special case that both recordings are from the same transponder.
The HDR-1000s extends this capability to any viewable 3rd channels.
When paired with this boxes capability to record the timeshift buffer contents, it becomes possible to in effect record 3 channels at the same time.
The third channel you are viewing can be recorded (from the beginning if you were tuned to it then) when the tuner being used to record the channel using the same transponder finishes recording by simply pressing the record button. In the special case of both recordings being from the same transponder, then the completion of either will allow recording of the viewed channel.
Tested this today
Channel 4 - HD 14:45-15:15 (11126 V)
BBC1-HD 14:55-15:40 (10847 V)
4Seven Come Dine With Me 15:00-15:30 (11126 V)
Pressing the record button at 15:20 (after CH4-HD finished recording) gives a full recording of Come Dine With Me.
I imagine single cable users will be able to do the same (with the obvious restrictions as to second channel recording).
The above example should work with a single cable as both recordings share the same frequency band (low) and polarisation (vertical)