I went to do a bit more cleaning today, I just learned how to move the slam panel to remove the cat heat shield. The shield is in poor condition so I took it off then took off the cat. There was a loose ball of ceramic stuff inside so I broke it up and removed it. Refitted the cat and the car drives very well. I think the oil is coming from the oil cooler or the filter housing. I ordered an EGR blanking plate in case the valve was sticking so thats next when it arrives. Anyway thanks to all you guys for your input. I need new heat shields, are they expensive new?