Thanks for the reply. I'm just suprising myself at how simple it seems to get this up and running. I did think that running the servos direct wouldn't be practical in terms of current - for an arm I was thinking of quite powerful ones as well - nothing exceptional but they would need a bit of oomph, not just small RC car ones. I wonder how much current they will draw? I should read up a bit more on servos - do they draw a constant current when working, or much more when moving and then it drops off?
If it's too much for all servos I can maybe run each in turn to get a final position, but I would like to try to get them running together - can't be too hard to get a power supply on the cheap to power them all. 