Splott,
There are a lot of factors involved in building a "CNC". Power supplies, motor drivers, software, resolution, etc,
By "pic" do you mean "PICAXE" or "PIC"?
Remember a PICAXE can process 2000 instructions per second. Do your calculations on the possible speed of the cutting head. You will be very surprised, BE patient.
If you are interested in a straight "PIC" version, GOOGLE "PICSTEP"
For a clever simple stepper motor application, GOOGLE "EGGBOT", seems appropriate for this time of year.
Myc