how can i fix my 1999 Clio grand 1.2?

three times my clio has stopped dead as i am driving over the course of time from new. It is serriously dangerous as when i tried to use the hazzard warning lights the doors locked and it caused trafic chaos. I had to wind the window down and struggled to pull the door lock button up, had it been a motorway i would have been killed along with others.
The battery showed 11.8 volts but everything was dead next day the car started without any hesitation.
the digital clock has been gaining 2hrs in 12hrs the offside head lamp has blown, the rear window demister won't work and when i lock the car, as of late the indicator lights no longer flash.