OK, so this is all very standard stuff but it's the first time I've played with a stepper so it's exciting for me, honest.
Something I'll have to deal with is getting the initial position of the pointer calibrated then keeping track of it. I'm currently thinking that I will make it return to zero before the device switches off. Alternatively I could write the last position to NVRAM occasionally but this isn't rated for a vast number of writes on Arduinos.
Next thing after this is to start on the physical build of the prop as the various electronic modules are coming together. I think my last worry is a power supply and batteries. I want to use two Li-ion batteries salvaged from a laptop pack to give it loads of poke, but they won't be easy to remove because the prop will be all sealed up and this will make charging them troublesome.