Hi Gerrywal, I did, and no it wasnt cut. These must be different dampners.
I have now cut the bumpstop and removed it. Once the stop is removed the damping adjusts as expected.
The mechanism engages when the dampner is fully in and allows three half turns. The first two dont appear to do much, in the last half turn it goes from "easy" to pull open to almost locked. The picture shows the dampner at fully open, note that the bumper is almost twice the height of the gap (and wasn't split). Virtually impossible to remove. So either I am doing something wrong or Koni put the wrong stop in.
Cheers J