Well to finally put this one to bed, I've found that in the real world the practical aspect of using the PIC in this environment, is not without issues. The main problem has been with the reliability of the PIC. Whilst the control at slow speed can't really be beaten even with commercial controllers, the PIC often falls over and stops generating the PWM signals and requires the power to be disconnected and re-connected. I'm not sure what causes this, but would suspect that its something to do with the noise that model railways generate, or the back emf or something.

The concept was great, I've gained a lot of information and found some nice new usefull routines and had fun playing with these circuits and code

how's that saying go... back to the drawing board