If the car's having it's first MOT it must be 3 years old - ergo it's out of warranty.

Nope, if it's out of warranty before you get it MOT'd then the test is late. A clever person will have an MOT asap, ie a month early, so there is a month left on the warranty and get problems fixed for free if they can.
 
Our LC has an advisory in the MOT from Seat, Barnstaple (N.Devon) for that bracket being broken but exhaust still properly secured.