Auxiliary DC Connector
The manual refers to this connector without providing any detail (other that to say that it's there and that a dealer should be consulted).
After this afternoon's fiddling about I can confirm that my early 2016 XSR does indeed have a little connector taped to the wiring loom. I have confirmed that it provides 12v when the key is in the "ON" position (and 0v when it is not).
YouTube shows how to find the connector on an MT-07 and a procedure for disconnecting it from the loom. Even with the rectifier and tank covers removed I could not really see the connector, so to be sure that I was in the right place I unbolted the rear tank attachement (2 silver allen bolts on each side can be accessed when the tank covers are removed) and pivoted the tank about 10cm upwards on the forward attachment point (as far it would go without putting any strain on the pipes and cables connected to the tank). This was enough to give the view in the attached photo. What the photo or YouTube does not let you see is that the 12V connector is quite a few cm deeper behind the rectifier that the other connectors that you see on the upper left of the shot. The red line on the shot shows the extent of both halves of the connector (the "upper" half is the part taped to the loom and is just a plastic shell to hold and protect the wired half). The green line shows where to (carefully) cut the loom tape and free the connector (before risking any damage to the loom when cutting the tape it's probably worth first trying to gently pull the connector from the shell).
My plan now is to use the connector to energise a relay for the heated grips I have installed - more on that another time perhaps...