I have the original version of the megane, so this may not work for you, but here's how I sort it what my battery connections drops out..
Use the stereo control stick beside the steering wheel, turn the wheel up/down to select the right number, press the search button to move to the next digit and repeat until you have the right code displayed. Hold the search button down for ~5 secs and it should accept the code and you will be good to go.
Kiltedsteel
February 2007