Took one unit apart and got the pin moving freely. However to do this I had to hammer it out the top. Lubed it, replaced top cap and assembled. Would rather have done it with new o-rings etc but hey, at least I know now how it comes apart.
Went to remove the other two units from the 'airbox' ? guess what, two torx came out with difficulty, third in both cases had to be drilled out. One pin jammed solid, more hopeful of the next one which is at least moving if slowly. Had enough for one day.