Just stumbled across this in the iPhone app store. Hitchcock is a “mobile storyboarding” app - you take photos on your iPhone and then drop in camera moves, stand-ins and audio. You can even set timings for the shots, so you can experiment with pacing.
At £11.99, it’s a little pricey, but it looks like it could save a hell of a lot of time. My draughtsmanship isn’t great, so an application like this could be very handy for me - looking forward to testing it out.