Thanks for the replies, didnt make myself clear, the manifold is knackered split, so your saying replace with a standard item?

The cat is breaking up inside and rattles to high heaven at 2k revs, its not the heat shield because ive taken it off already. If you give the Cat a tap from under the car the noise can be emulated. As yet no warning lights on the dash, ive got paperwork regarding the changing of at least one lambda sensor by a previous owner.

As for passing MOT's you just need a sympathetic and knowledgable tester, they will rev the car to 3.5k for the emissions test instead of 2.5k. Did that with the FRP which is also prone to failing MOTs on emissions.