Thanks Gents. I gather from the replies that there is no mysterious and usually encountered gremlim I should be looking out for then.
The next thing then is to check what I have against what I should have. Since I am not running out of thread on the spindle it must be the fitment of the ball in the cups. The steering turns without being notchy at all so I will have a look at the balls themselves. I know the bike was stripped completely before I had it and I would say that the cups would be a less likely /easy thing to renew than the balls during any renovation.
You can see a lot of ball when the arrangement is supposedly tight, to the point where I suspect that they might fall out. OK thanks for the feedback. the picture is becoming clearer.