I'm pretty sure the "select camera at any time" function is not available in preMY14 models Andrew. It is same update that provided a CANBUS connection to the rear camera to provide the "bendy lines", which I cannot get as my camera is from a pre MY14 model.
There may be extra video feed inputs in the back of the screen unit, but they will be meant for video playing and so will disable when the vehicle is in motion. Your only other option may be to access a camera using the "secret (service) screen", though this screen will not stay on indefinitely and to bring it back up again you have to got through the 30 seconds button push routine again.
The above should be confirmed by someone who owns a preMY14 model though:angel::angel:

