Just bought a NC30 how do you gain acess to the battery ? under the seat maybe ?

It's pretty straight forward.
Remove the pillion seat
Remove the 3 fixings on either side of the tail section
Gently lift up the rear (by the brake light) and unplug the little connection for the rear lights, on the left side.
Slide complete unit back and up, you might need to gently persuade it past the rectifier

Job done!

Spot on thanks

Paul