How can I fix my Renault Megane Authentique?

My Renault megane won't start. (2002) the battery was so dead radio code came on and flashing red light was off, no central locking, was using keyhole in passenger door to get in and jump starting it. Bought new battery, but remote key does not work, have to manually unlock to get in. Engine turns over fine but car refuses to start. Electric windows not working as well as other things. Help!

Dave
February 2017