I sunnie and welcome to the forum
Try the below, it should help. Not sure which type of key you have. This was taken from another post by the way.
Hope it helps.
MEGANE RF RE-PROGRAMMING
Hold the remote control button down for longer than 10 seconds (until
the red tell tale light on the key extinguishes) then press it again 3
times. Check that the doors lock and unlock correctly.
MEGANE WITH EARLY REMOTE (LED SWITCHES OFF WHEN HOLDING
1. Igniton ON
2. Press and hold the central locking button for 5 seconds
3. LED on the dash board will go off, come back on and begin to flash.
The flashes correspond to the first digit of the 4 PIN security code
release the button when the first digit has been "flashed" and then
press the button again.
4. Wait for the second digit to be "flashed" then release and re-press
the button continue until all digits have been entered.
5. If you have entered the code correctly the LED will then go out and
the car can be started to code the remote, switch off the ignition and
press the central locking button again.
6. Press remote button 2 times within the immediate vicinity of the
pick up (in the roof). On some vehicles you may need to switch the
ignition back on to achieve this however.