Now, the smaller bearing turns out to be slightly too small (nothing is ever perfect) so a limited amount of fettling is required. I just had to take about 0.5mm off the edges of the triangular shaft (which mostly consisted of my POR15 painting attempts)
Here it is pictured on the shaft just to make sure that I had fettled far enough to enable it to fit.
I can't fit the steering shaft in properly until I can fix the scuttle back in place, which is after I've done the side panels...