When I set Q_MOT_SPIN to a value high enough to spin my motors on arming only motor #1 (front right) spins. I would expect all four motors to spin like they do in copter.
This was a simple case of not calibrating the ESCs properly. Turns out I was waiting too long when applying the power which was causing the ESCs to go in to programming mode so I was just entering and exiting that mode rather than calibrating the throttle range. One of those ‘Doh’ moments.