How can I fix my hild locks on 52 plate Renault Megane Dynamique DCI?

Child door locks and window locks are on same switch on driver side door panel yet only the window locks are working!? My husband has checked fuses and all seems fine. I really do not want to have to take it to a renault dealership and get ripped off, as we all now pennies are tight! Any suggestions or ideas would be great, especially as I am desperate to finally get my 3 year old in to a booster seat without the risk of a great escape attempt!