I put the GPIO pins for my senseHAT the opposite way round (so that the senseHAT was facing away from the pi). I powered the RPi and when I tried to handle it I got slightly shocked by the senseHAT. I tried one cable and it didn't launch (I think it might be the cable though). Should I be trying another cable?
UPDATE: The socket is a 2.5A 250V iPad socket. The cable I used is a standard USB to microUSB.
UPDATE: It's working now thanks guys.