What is wrong with my Citroen Xsara dashboard?

There is an electrical fault in the dashboard of my Citroen Xsara. Sometimes, when I turn on the engine, I get warnings- ABS system failure, Brake failure, Low oil warning. The dipped lights show as on but none of the lights actually work. Indicator, speedometer, radio don't work. After messing with buttons for 15-20 minutes the indicators work but the speedometer takes longer to come back on. The car drives but the radio doesn't work at all. The mechanic suggested changing the dashboard but I am reluctant to do this because the electrician couldn't find the fault- the car was at the mechanic for a whole day and was fine then. Has anyone experienced these problems?