key wont work with central locking on my clio?

My 2000 clio is locked, and the key remote will not work with the central locking. Because the door locks have never been used through the years, they are also well and truely siezed up! so i am un able to get into the car. I have changed batterys in both keys. One key just doest even light up when pressed, but the other key does light when pressed. Would rather not pay a fortune to have the key coded back in. Does any one know of another way to sort this?