When replacing broken part part on end of key barrel, you need to ..

Take door card off

Take two nuts off back of handle

FROM outside you can now carefully pull handle bolts out Which are part of door handle.

At this point you can see both wire rods leave on for now and rotate handle90 degrees or so

You now can get at broken plastic part , take rod out of this one leave the other in place

What looks like a rivet on end of key barrel is in fact a  E CLIP Use small screwdriver and release this 

Take broken bit off and clean end of barrel put new metal type on and refit E CLIP

Now refit rod and rotate handle back to original position manoeuvre  back into door 

Refit both nuts

And test. 

Metal replacement was bought from CZP as a pair they sell new plastic clips also. About £20

Hope this helps 

E CLIP and old plastic part

Thanks for the writeup. I would add that it is worthwhile masking around the door handle aperture before

starting the handle removal/replacement to protect the paintwork.

Before I order one from CZP does any member have one for sale. Metal or plastic.