Thanks Andy - interesting! Tony Griffiths suggested it was a TS E-Type fitted with an S-type vertical head. The motor is 3-phase - but the whole system cleverly runs from a 13 amp 240VAC socket. There's a lot of electrical and electronic control stuff in the upper main structure which makes this hap...

I've just bought a beautiful Tom Senior with Vertical Turret in excellent condition - but am not sure exactly what it is.
Here are some images.
Can anyone help?
Thanks,
Steve