Had a moment, ducked home (I work literally 5 minutes from my house), and got it off. I held the bolt in the socket, in a vice, and used a shifter on the catch. I did it that hard that the starter flew out of the vice and crashed on the garage floor. Oops I bet that stuffed it. But no, I could now undo the catch bolt and hold the nut with my other hand! It must have been a bit seized up and the jolt allowed it to work free. The spring was a bit rooted, but I saw how it had a hook that faced the centre ring. Cut off the stuffed bit, recurled a new hook same as the last one, but right against the centre hole, put it all back together (that clip with the loop threw me off until I checked the gregorys). Screwed it up, with the starter cord wound on and last bit in the little notch, pulled it through, put the handle back on and another knot to hold it, and using a spare big o-ring I had ordered earlier just in case, it is back on the mower and working like a champ!
Next up; Carby time.
