Thanks for all your help. I also found the information on this web site at Lotus Parts Bulletin: Dellorto Carburetters which specifies a rod (A036 E 6144Z) that appears to be the original part.
On trying to find locate this, my mechanic spoke to our friendly TwinCam expert who said ‘Why would you want to do that?’. On the basis that I haven’t needed the choke yet, I’ll leave this job for now. If it aint broke…
Cheers,
Gary.