I have bought a 1.1kW 3-phase motor for the mill, 2800 RPM 2 pole. I don't think the 2HP motor is going to be necessary (24mm shaft diameter!).
Just to be safe I went for a 2HP capable VFD to run it. The added bonus of all this is that running the speed from Mach is pretty easy. I'll post when it has arrived and is all mounted up on how well the system works.