brava 100bhp diesel water problem

hi all, does anyone know if there's a special way to bleed the heating system on the above vehicle, the header tanks full but the heaters are cold, or am I clutching at straws because I know it's the head gasket ? engines only done 102k, it starts first time but it does boil over after a few miles, the reason I ask about the heaters is, I had a diesel rover with the same fault and it turned out you had to bleed the heating system in the correct way or it boiled up. are head gaskets a common fault with this fiat engine and what are like to do ? or is there anything else that is " known " problem ? any help appreciated thanks in advance daz or does anyone want to buy a 1997 p-reg fiat brava sx with a full years mot, some service history, metalic paint going CHEAP. daz