Just to close this off... I went to the Scott dealer here who happen to have the best techs. There they said as dsaul says above you take the sleeve off - they key thing is to have the measurement of the cable absolutely spot on.
So now I get to take the external dropper off, sell that and put the original internal dropper on like I wanted.

Moral of story - get a second opinion and don't get a roadie bike tech to work on an MTB?