I was a bit concerned that my choice of the lightest set of cobalt flatwounds were too light to pull any relief into the fairly chunky neck of the bass, but I've just given the truss rod a further tweak and managed to get more relief than needed, so I dialled it back a little and it looks like that has done the job.
Now when I press down on the first & fourteenth fret the gap between the string & top of the fret nearest the midpoint is about the thickness of a business card which is what I was looking for. I'll let it settle overnight and check again tomorrow, then I should be able to finesse the action and intonation at the bridge.
The method of adjusting the string height on the babicz is a great piece of engineering that works really well. setting the intonation is a bit of a faff as you need to loosen the lock bolt in front of the saddle, and if you don't slacken off the string, the ball end gets in the way preventing the screwdriver from making the adjustment.
Given the choice of the Hipshot Supertone or Babicz, I don't think there's a wrong answer and I'd probably have been just as happy had I gone for the Hipshot.