I'd still like a copper set

Thanks Ken,thats a similar carb to mine.The shaft that the spring rests on only has one groove on my carb,whereas yours has two.I have tried putting the spring as in your picture,but it only comes into play when the choke is half on.Also,I have noticed that the choke butterfly is sprung to the on position ,surley thats not right.

Dave,
both the actions highlighted are correct.
If you check again, the fast idle cam may be half way through its range of travel when the tab contacts the spring, but at that point the choke flap should be 2/3 to 3/4 closed.
The spring acts to move the choke flap to the 'on' position, following the movement of the pin/peg on the fast idle cam.

Unless the early 30 PICS or 34 PICS carburettors were arranged differently, but I doubt it.

ken