Slightly older engine but the 320d Compact in the family was bought at 45k miles with full BMW history as an approved used car, within 6 months the compulsory turbo failure happened, the dealer replaced the troublesome first generation engine breather whilst dismantled.

That car had an oil change, by me, with good quality oils and filters every year, around 7k miles for all its time with the owner, around 110k miles there was a noticeable rumbling in the area of the head or timing chain which no longer went quieter after an oil change, so part ex'd it was.

I'm sure part of the problem is that some of these engine designs (PSA 1.6 Diesel is the same) do not drain fully at oil change time, because 2 minutes after an oil change the oil is filthy, i changed the oil in my 90k Landcruiser couple of weeks ago and 500 miles later its still so clean its difficult to check the level without me glasses on.

If these engines are not draining well, does it suggest to anyone else that carbon nasties are being held in pockets all around the engine ready to immediately mix with the fresh oil, an they gradually form the good old black death mix on many surfaces that we thought was a thing of the past, or is it me?

Manufacturer's service intervals are sales pitch, intended to impress the consumer that this/that car will do xx,xxx miles or x number of years between services. Anyone who knows about cars, knows this is nonsense. None of us use our cars in absolute ideal conditions, and the more we don't the shorter the actual service interval should be. The longest anyone should go between engine oil changes is 12 months, regardless of mileage, and even 6 months is preferable. The single best thing anyone can do to keep their engine in good condition is to change the engine oil and oil filter regularly.