Punto overheating?

Hi
The temperature gauge on my punto went into the red today and there is no heat coming through the vents in the car, last year in Sept I had the same problem then I took it to a mechanic who said it was the head gasket he then replaced this, the car has run fine until July this year when the problem reoccured I took it back to the same mechanic who said it was the water pump this time he then replaced this, the car has run fine again until today where the problem has returned I have taken it back to the mechanic who tested the cooling system and found I have exhaust gases in it. He has tod me the head gasket has gone again, I have only covered 4000 miles in the last 12months so surely this can't be the fault again. He has said that when the water pump broke in July it has blown the head gasket and it has taken till now to come to light. Could this be the problem or was the head gasket fitted incorrectly back in Sept 08?