Big thing will be if the motors have quadrature output encoders, or resolvers. If they have resolvers, then you're looking at a conversion to encoders, which can get pricey.

Voltage wise, there will be various transformers for providing the voltage to the drives. They likely take the 380V and step it down to 240V. The ideal thing would be to power it up using 3 phase, then measure the voltages. You have to be aware they may use what seem like non-standard voltages (i.e. 208V), which won't work directly with UK mains voltage. Also if you bypass the transformers, you'll likely loose isolation.

Keeping the original drives, you're looking at needing an analogue (aka +/-10V) capable controller. Cheaper options are CS-Labs CSMIO-IP/A, Dynomotion KFlop+Kanalog, or whatever the LinuxCNC option is.

Swapping motors/drives does open up more options.