This evening I removed the motor from the machine as I’d found a company in Warrington who could rewire the motor to 240v three phase from 400v three phase. They also sell inverters and various other bits, and I plan to purchase an inverter so I can run the lathe from my 240v single phase supply.
For anyone who doesn't know, an inverter can convert single phase domestic 240v to three phase 240v, so rather than buying a new motor you can instead buy an inverter. That said, inverters tend to be more expensive than new motors, but one of the benefits is that with an inverter you're also able to run the motor at any speed you wish, which for a lathe is a real plus.
Tomorrow I'm dropping off the motor in Warrington to have it converted.