How do i find my missing radio code. Peugeot 306 Maridian on a Y plate?

Hi, Can anyone help me, I have moved to France and had to change my battery, oops I forgot to find my radio code befor I disconected. only to find the small book with the code in it does not seem to have moved to France with me now how do I get this radio working again without having to buy a new one? any ideas please. Terry, retired to France