had a look at the diagrams. so a fair amount of lean/rich adjustment can be made without getting different needles?

yes.
Also you will have seen that the needle taper makes a difference too as it is carried by the side out of the mouth of the main jet.

raising and lowering the needles is a simple way of making taper adjustments without needing new needles.

I though I had it sorted but of late my bike is running like a stinker. Must go get it sorted...