How can I fix my central locking on my T reg 1.6 VTR Citroen Xsara?

Hi

When I lock the car from the drivers door with the key - I have no remote central locking - even if all the doors are shut, only the drivers door will lock.

I can lock the boot manually, but the passenger door won't lock at all! I've even tried locking it from the inside, then locking the drivers door but nothing seems to work!

Thanks