>>> "closed loop stepper in torque mode" function seems to be a bit of a minority sport.

Yeah, I think so. And I didn't realise the preference for servos for this application although that makes sense, so thanks everyone for that.

>>> it's not clear what the OP is actually after

I should have said: the application is a clamping one - needing to produce a given clamping force in the 1-5Kg (~10-50 Nm) range and constant over a variable distance of ~5mm or so. There is a requirement to start at a particular distance (hence my 'stepper thinking') but after that it's a 'closed-loop clamping application'.

Alan