Hi Alain and others,
Thank you all for info given, it is much appreciated.

Alain, regarding the linear problem - I have tested the actual distance travel of the servo arm by connecting a ruler to the arm.
To test I then adjusted the speed voltage, taking voltage readings and distance readings as I go along.
The distance values on Excel graph showed a non linear line in comparison to the linear nature of the voltage.
/Daan Joubert