Just a thought - have you checked the oil feed hoses (I believe they're the turbo feeds) at the very top back of the engine block (you need to remove the plenum chamber to access, and you won't be able to see, so will have to feel or use a mirror or camera)?

The o-rings on these eventually fail and the oil works it's way down onto the bell housing where it burns off. As it's directly below the cabin air intake, it would be easy for the fumes to get in the cabin.

Quite a straightforward fix, but is done blind. 2015 Range Rover Autobiography 4.4 SDV8

Hi Jay, did you manage to sort this issue out? Ive just had my oil cooler done and changed the coolant with a new reservoir. The next day i got on the m way took it for a blast slowed down into traffic and getting loads of smoke coming into the cabin! Ive had the garage check it out again they are not sure

Its coming up to about 4 weeks and Ive done 800 miles since however i is still doing the same thing 😑