I have upgraded a Denford Novamill to Mach for a total cost for components of about £200. This was for 3 stepper drives, psu, BoB. I already had a spindle speed control, that would add about 100 quid. Used the original steppers. Computer also I already had. But I did all the work myself, I don't know anyone who would do it as a service. It isn't that hard, you could buy almost everything ready made from Roy Harding at http://diycnc.co.uk/html/cnc_systems.html.