Peugeot 206 - central locking?

I have a peugeot 206 and recently the electrics have been doing strange things mainly my central locking. Two weeks ago i switched engine on and doors locked but was still able to open from inside. Today i started engine and doors locked again but didn't make the noise of locking doors and i was unable to open from inside. I tried using the central locking button to lock/unlock doors but no such luck. The boot opened from the outside and the electric windows worked fine. The only way i could get out was by someone using key from outside. How can i get this fixed???