JUST GOT A RENULT MEGAN 1.6 COUPE ?

We have just changed the battery in the car as the immoboliser was playing up, but that has knocked the radio off, now we dont have a code. We got this code from the back of the radio - RN481FX9204305, but there is no other stickers or information on the radio to help.

The radio is a phillips, but dont know the exact model.

Anyone know how to get the code or what it is?