Replacement cooker faulty after initial 12mths HELP!!!

We purchased a cooker from argos, 29/8/07 and then after 4 visits to try and repair it they replaced it on the 3/3/08, now the replacement has broken down with the same fault. I have phoned argos saying that we would like a relacement as the sale of gods act says they are liable for 6yrs after the initial purchase. They have then said to us that we need to get and independent report (and pay for it ourselves) stating that it is a manufacturing fault and send it too them and we may be able to have it sorted. Is this right? Can anyone shed any light on this and where we can go from here, we would appreciate some helpas we are not in a position to purchase a new appliance, many thanks lynda.