OllyR:
I want to program it so that turning the Pot to the right, makes the servo turn to the right. However, turn it further to the right, and the servo turns to the right faster! return the Pot to central, and the servo stops where it is.
to get it back central, you have to turn the pot to the left.
Kind of like steering a car?
Hope that makes sense.
That isn't a standard unmodified servo. It sounds like you want to modify the servo to do continuous rotation. Here is one such article that mentions how to do the modification: How to Build a Robot Tutorials - Society of Robots. You can also buy modified servos from various robot shops. For example, Pololu - Parallax (Futaba S148) Continuous Rotation Servo #900-00008.
I believe a modified servo uses 90 to stop, and 0..89 for rotation in one direction, and 91..180 in the other, which sounds like the behaviour you are seeing.