Inferior windscreen quality

We had our windscreen replaced in 2011. Subsequently from about a year later small spots started to appear on the windscreen. We took the car back to PG as the spots have become so bad you can hardly see out the windscreen. We were informed that the glass 'layers' are separating. The assistant ageed that the product was inferior and this should not be happening. They contacted Peugeot, the supplier of the windscreen, who said they only gaurantee their products for 6months. Neither Peugot nor PG who provided an inferior product to us have taken responsibility or assited us with a replacement. I feel PG glass chose this inferior product on our behalf and surely the glass quality of a motor windscreen should last many years?