Anyway, I subsequently found the spring in the footwell, didn't recognise it, assumed it had fallen out of some part of the seat (I'd had that out during the work), and put it to one side while I dealt with the emissions problem. On my way to that fateful contrôle technique appointment, I did notice that there was something wrong with the gear lever, wondered if it had something to do with greasing all the linkages, and then the knob came off in my hand.
At that point, seeing the size and shape of the stem inside, it suddenly made sense as to where that mystery spring had sprung from - so I popped it back into place, jammed the knob back on and all was well with the world ... for about five minutes. A rough bit of road was enough to loosen the knob enough for the spring to fire it off down the back of the camper. The problem recurs every time I try to re-fit the spring, and a bit of blu-tack in the knob isn't good enough to hold it, so I've left it off again (can select first or second by consciously pressing the ring down). So I'm thinking of fitting a grub screw to the knob, drilled into the shaft, but before I start cursing and swearing at the awkwardness of the job, any suggestions for a "good enough" glue that'd resist the force of such a spring while driving over cobbles, but still allow the knob to be pulled off in the future if ever I need to work behind the dash again?
