Thanks for your help both.

Next time I ride I will see how smooth it is when I pedal lightly as I change.

Are more expensive gear systems better than cheaper ones in this kind of area (smoothness and accuracy of gear changing) or are they pretty similar?

I think ultimately I need to change the gears about a bit anyway, because I only use the top 4 gears. I assume it would be better if the most used gears were in the middle of the range?