renault key wont start car?

hiya i have a 1.4 16v Renault clio. it recently stoppped starting and the central locking wont work. i replaced the cars battery but still no luck. i messed with the key fob and replaced the battery and it worked for a few days (central locking aswell) now it wont work again and i have also tried the spare key but central locking wont work either. any help? email address is