I've found a steering wheel boss to fit the BMW column. Couldn't find one that would fit my Mountney wheel - that has a 100mm (4 inch) 6 bolt fitting. All I could find was the more modern 70mm 6 bolt fitting so I've had to buy a wheel too. If any of you want a 14" Mountney classic wheel let me know.
Anyhow - here are a couple of pictures of the new wheel in the car. It's a replica OMP Corsica wheel off ebay.