This is now rectified. My mechanic sliced open the exhaust and found a solidified peice of cat internal had broken lose and lodged itself around the rear of the cat perfectly blocking the flow of gases...the car would not even tick over!
After welding back up and resetting the fault code it seems to be running very nicely again. He said there should still be enough filament left to not trigger the EML and after 6 weeks of driving It hasn't yet.
Whilst it was off the road I bought the wife a brand new Smart forfour Edition Black. My neighbours laugh as we have the biggest and smallest cars now
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2002 S8 - Irish Green Pearl. Cat N (saved by the D2 Doctor

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1988 E30 Coupe - Royalblau Metallic
2003 S4 Avant - Light Silver Mettalic
2016 S5 Coupe Black Edition - Glacier White