My steering felt notchy but I thought I'd just wait till winter to replace the bearings. That was about as serious as I could be bothered with, but now that I have replaced the bearings the bike has almost transformed in a few ways - some wallowing in corners that used to occur around 120 kph is now gone ! Beautiful ! Interestingly, a mate who used to race told me "if it feels like it's from the rear, it's most likely a problem with the front", he was right.
Next thing that's improved - straight line tracking at slow speeds, around 40 kph I used to feel like I needed to constantly correct to stay straight. This was the central notch locking the steering minutely, a bit like trying to ride a bicycle with a welded up steering head, which is not possible.
So, a couple of learning I will share -
Bearings - 2 off 320/28X SKF or FAG (or Timken I guess) No need to go genuine as the BMW items are bog standard SKF items.
1 new lower metal cup (BMW part)
Good quality grease, extreme pressure (EP).
Spend plenty of time packing the bearings with grease. It needs to be thoroughly worked into the inner cage cavity so that when the steering is turned the rollers push through lubricant. Don't over pre-load the bearings on assembly. Remember, when the top nut is locked down onto the large knurled one, the clearance is removed from the thread and the preload increases, so you need to check the feel after tightening and if necessary, back off a little and re-tension. Take the time to get it right and the result will be worth it.

Thanks for this.
As a reminder, I posted a cross reference chart for bearings here