Discovery 1 Exhaust Part Systems - Petrol
Listed below are part systems for catalyst and non catalyst equipped vehicles.
Catalysts are normally quite durable, so it is unlikely that you need to replace the full system including catalysts.
An MOT emissions failure or a rattle will usually indicate the need to replace the catalysts and perhaps the full system.
Likewise, downpipes on EFi non-cat vehicles can have a long life, so you may wish to consider replacing the system rear of the downpipe(s).