Well there were a few problems getting it to go. After much swearing and changing of configs in Mach 3, it turns out that it was a parallel port issue.
The controller interface requires 5 volts which it expects to get from the parallel port but my PC didn't provide the correct voltage/current.
Connected a separate 5 volt power supply to the interface and all was well.
There still tuning of the motors to do but that will have to wait, off on a sailing weekend tomorrow!