How old mate? it's always worth giving them a ring as see if they can help you, you never know.

Generally I hate dealerships with a passion because of warranty's, I have many annoyed customers come to me with exhaust problems because the dealerships riggle out of it, they find any loop hole!, if it states it isn't covered then your be hard pressed but like I said have a word with them as technically it would have had to passed an mot and if there is a hole in the exhaust due to corrosion then it's unfit for the road as crazy as that sounds, I had a customer take my local ford dealership to court over the same issue and he won on the grounds the car was suppose to be sold in road worthy condition and it wasn't.