In reply to The Potato:
As others have said, no point changing the exhaust just for the sake of it because the car is coming out of warranty. Only reason to change the exhaust is if you are modifying the car and need a bigger exhaust as you are increasing the power or you want to change the noise the exhaust makes. Otherwise, leave it till it needs replacing due to damage.
If you do want to change the exhaust, again, unless you are trying to boost performance I certainly wouldn't change the cats as one, a decent set of cats is going to be in the high hundreds of pounds and two, with high performance cats or cheap cats you run the risk of failing the MOT emissions test.