Hi there, we have a little mini cooper s on a 2003 plate. We have no reverse light

Have tried replacing the bulb but with no success. On reading the threads i have decided to try changing the reverse switch. Now got my switch but i cant locate it near the gear box. I have had the airfilter and bits out today but with no success. Didnt no if any body had a diagram of where it is? Any help would be really appreciated. jonny