How do I go about replacing a burned out bulb behind the "Heated Seat Button"?

I know loads of other threads talk about headlight bulbs but they all seem to be about mods and extra bright bulbs etc. All I wanted to know was why I was struggling to get an H13 bulb (as the book states) and also why Halfords and Jeep recommended H4? H4 is easy to get at any carshop where as...