Thanks for the comments - unfortunately I don't have a Pi3 and the object of the exercise is really to get it on the Pi Zero in order to make an all-in-one hardware/software dev environment.
I've never tried compiling the Arduino SDK from source but if it's possible on the Pi Zero (albeit taking forever as you say) I'd happily leave it running non-stop.
I'm supposed to be doing an informal demonstration of the ESP at next months Raspberry Jam if I can and hoped I could put some stuff together using Arduino sketches. If it's too much hassle I'll resort to NodeMCU / ESPlorer and Lua.
Cheers,
Brian