Fiat earth fault

My fiat punto sporting (04 reg) has developed a fault-am guessing an earth fault-when headlights are off and I use indicators, the headlights and dash lights flash on and off. This doesnt happen when headlights are on. Today the heater fan has stopped working also. Have checked fuse and it has blown. It was in garage last week for a new emissions sensor. Could it be related? What can I do? How do I check the earths (am totally non mechanically minded-a woman-and too skint to take into a garage!