Just to update this thread. Have just used a breadboard PSU with 3.3v on the Vin pin and hooked up the ground.
All worked perfectly, unfortunately onion doesnt fit my breadboard as its too small!
Just for good measure I hooked up an LED (with resistor in series) to the GPIO. I used the console, gpioctl and fast-gpio to turn it on and off and can report all worked :D