Just a quick update to my circle cutting problems.
I basically have not idea how or what fixed it but the changes I made were:
1. Fitted a SmoothStepper
2. Fitted shielded cable for the spindle motor from a junction point to the Spindle motor.
The smoothstepper has allowed me to increase my resolution from 143 pulses / mm to 259 without sacrificing speed and the shielded cable was what I should have fitted first time around.
Thanks to all who responded, I have been cutting perfect circles all weekend.