General MOT failure question

Hi, I have a vauxhall astra and I have a query on its recent failed MOT.

The MOT Failed on (amongst a couple of other bits):
* Exhaust has a major leak of exhaust gases (centre to rear) (7.1.2)
* Exhaust emissions Lambda reading after 2nd fast idle outside specified limits (7.3.D.3)

but my question is:

Last year on the 30/06/15, by the same garage, they fitted a new flexi pipe, catalytic converter, gasket & clamp.

Is this the same thing? Wouldn't that of been under some sort of warranty if it was?

I have no idea about cars and hoping you can answer this query before I get my £15 from the scrap man. :-(

Thanks in advance
Brett