If you go to
[Please Register or Login to download file] and look at Section 23, it says this "Can I delete the data I installed my navigation system?
You can delete all data from your GPS system, with the file Citroen Risk Areas - Clearing your radar, this file is used to reset your navigation system in its original configuration by downloading a file completely erasing your data in radar the installation file on your system.
The installation follows the same procedures as the installation of another file Citroen Risk Areas."
I seem to recall that there was a file you could download from the Citroen site that would clear the system. I think there is also an option on the car itself where you can reset the system.
Have you looked for that?