Ian,
I have put together a simulation showing how to take a differential signal from either the CXD3782 or LM27762 and inputting the differential signal into the OPA1656 to convert to single ended. The simulation can be found at the bottom of this post. You can see that the output voltage is equal to Vout = (Vout P - Vout N) + Vcm. I have this setup as a single supply system. You can make it split supply however and move Vcm to mid rail or 0V if desired. In addition I have a link to a handy article on the math if the resistors are not matched as I have done. This can also be found at the bottom of this post.
Below you can see my simulation results for the circuit.
