After many unsuccessful attempts at working the stepper motor I came across other projects using the Raspberry Pi that connected it to the servo and speed controller of a radio controlled car. Although in total more expensive and less customisable, it would save me plenty of time and effort to create the rover itself this way.
The biggest drawback would be the battery life. The rechargeable battery pack for the Pi lasts about 6 hours but the battery for the car is supposed to last only 15 minutes. I guessed it would last longer however because I would only be using it in short bursts of less than a second at a time, and the ESC would be drawing power from the Pi rather than that battery.
I chose a 1/18th scale model because it is smaller and therefore will have more room to move around.
After purchase the first thing I did was connect the servo in the same way as the one I was planning on using to move the camera with. This worked fine, however, the wheels obviously do not turn 180 degrees in each direction so I had to adjust the pwm time so that it would turn the wheels up to a maximum of 45 degrees in each direction. I also upgraded to a metal geared servo to stop the gears from shredding so easily if it was trying to turn too far in one direction or the other.