I'll definitely be replacing and cleaning those CCV parts identified by stiubhartach - many thanks for the pictures and further info.
But for now though, my smoking issue seems to have been cured by a process of trial and error, using quantities of gradually thicker oils in sequence, as follows:
1) pre-insp. II - no smoke evident
2) post-insp. II and fresh Castrol Edge 5W-30 full synthetic oil - big clouds of blue smoke after extended idle
3) drained out 4L of oil and replaced with 4L of Shell 5W-40 full synthetic - still moderate smoke after extended idle, maybe a little less than before
4) drained out 5L of oil and topped up with 5L of Penrite 10W-50 full synthetic oil - no more smoke!

I now plan to run the engine on this cocktail for 5,000 km/3,000 miles, then dump it and refill with 8L of fresh Castrol Edge 5W-40 Titanium, full synthetic.
Will report back the results.

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Current:
2004 X5 4.8is - Le Mans blue/Cream beige
1994 E31 850CSi - Sterlingsilber

Previous:
1987 BMW E28 M5 - Delphin-metallic
1976 BMW E3 3.0Si - Arctic-metallic