After googling my problem and reading Frank Kinlans blog where there was conflicting adviceI think I have come to some understanding of what is happening.
I created a route on 'ridewithgps' and saved it onto my desktop as both a gpx file and a tcx file. I then copied both across to the Garmin Course folder. Only the tcx file shows up in the 'Training, Course' folder.
Next I copied the gpx file into the gpx folder. I found that on the Garmin under 'Where To, Saved Rides.
From what I gather the gpx file in the Where To, Saved Rides folder will give me a lot more information about the route than the tcx file in the 'Training, Course' folder. However, that is for another day.