Robbirch

I bought a 60 plate C5 on Friday and it already has to go back to the dealers as the stereo and My Way sat nav just go through and endless cycle of turning on, freezing then turning off again every thirty seconds. When it goes back should it come with an SD card in the slot for the sat nav to work as it didn't come with one but was sold with the description of having built in sat nav? Other threads on this forum would suggest it needs the maps on the SD card inserted to work.