Got it done in the end, not with the method in the video though.
First you need to get it so the clutch wheel (not sure my terminology is right here) can rotate through a full 360 degrees without getting stopped by anything. You do this by by ensuring the lock claw (again not sure on terminology) sits on its pin, and not above it as it is by default.
Then, start to rotate the clutch wheel, the further you rotate the more it tensions the clock spring and the harder it gets, i manged to turn it a full 360 degrees by pushing it with with a screw driver. Once there hold it under tension, and with the other hand fit the cable into its mounting.
Hope that helps somebody else.