battery light and warning beep?

Hi everyone - did anyone solve the mystery of the battery warning light??? just as i decided to sell my c3 pluriel I have just had the battery warning flash and beep after a mile or so. bit scared to drive it at the minute but with 2 small kids would be lost without it! I was going to get an alternator but after reading the posts I'm at a loss to know what to do :( can anyone help?