Thank you everyone who has given good, useful advice to this novice. In the end I had to take the wheel to the shop and they had everything all out in a jiffy, cost a fiver too.

What I have learnt here is that I never realised that the spacer is so much narrower than the inner hub. It has been an interesting learning curve.

What I did notice mind, was that the bearings had what I'd call "groves" between the inner and outter race. This may have been the bearings pushing into the spacer, to the point that the spacer could not move. The bike shop macanic did "go a little red in the face" while doing it...bless him.

The new bearings are in and all seems well...