Roger Hayter wrote:

You are better getting a mains [switch] in the right (physical) place.

You mean the right place for conveniently switching the lathe on and off?

So I would route the incoming mains supply through a switch near the lathe,
then away again to the PSU and back as a direct DC 24V supply to the speed
controller (also conveniently near the lathe) and then the motor?

And, as someone else said, you can get one
of those red and green button ones that locks
out if the mains is interrupted so the motor
does not come on unexpectedly if power is restored,
and with a big red 'off' button.

I'm not familiar with them; I'll investigate.

Thanks.