How do you connect a single phase motor to a three phase power supply in UK?

for countries in Europe and other world areas running a 50 Hz supply service. UK household AC power mains voltage is now 230V (previously it was 240V) 50 Hz. From a 415 volt 3-phase incoming supply you will get this voltage between any ONE line and the Neutral.

Between any two lines you will get 415V. DO NOT WIRE IT LIKE THIS!

So, if you wire the motor to any ONE line (and ONLY ONE) and Neutral you'll get the correct voltage.

<><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

+++

My advice would be to buy a proper transformer which can be connected to a 415V 3ph input and give 230V 1ph output at a current rating suitable for the motor and its purpose. I assume the questioner's installation is in a commercial premises because domestic supplies in the UK are 230V 1ph only - running a 3ph motor off that requires a suitable inverter.