The new cable worked fine - the X, Y and Z homing switches all registered when hit, so it looks like nothing was zapped.
Had an interesting initial moment when all of the stepper motors where initially running in reverse despite the wiring of them being the same as in the instructions diagram, so I just flipped the green and black wires on all of them to get them running in the right direction.
~ new wiring setup
As a side question, after homing the X (right at the end of the video above) it moves away from home then back again with a chuddering motor sound - does this sound normal to those who have been up and running for longer than me?