For a given total spend you will probably be able to get a better spread of power, torque and speed using a 3 phase motor with the right power and gear/pulley drive ratio but that will probably cost more than just replacing your DC drive.
Thanks Nick, I already have an inverter but would have been a pain swapping the motor as i needed a 100x 125 mount spacing witha 14mm shaft which meant a new pulley or fudge the mounts.

Ive picked up a cheap sprint 400i DC controller which has isolated inputs so I will stick with the DC to get it up and running and learn with, then upgrade later.

Thanks