So, given that I've been playing with servos it seems that producing something simple to drive them would be a good idea.  If you are of a mind, and fancy  a modest challenge, then over HERE (in Github) is the source for the Arduino firmware.  This, after relatively limited testing, should work on a Nano, Uno or Mega2560 and control as many servos and the board has PWM outputs (with some reasonable exceptions).

Here (and arguably meaninglessly) is a picture of an Uno operating a single servo:

What this *has* shown (and provided justification for writing the software), is that I need to adjust the chassis design:  The Servo "pokes through" the mount a little too far (1 - 2mm) and so things catch on each other.  Back to the CAD again, and another 3D print.

I should add that while driving a single servo directly off an Arduino isn't a problem, driving more might be.  If you were to employ this then you would need to provide 5 volts for the Arduino (using the barrel jack or Vin and GND pins), and this power supply should be directly supplying the Servos with only the control wire linking the servo to the Arduino.

Jeff/