Thank you to all responders to my original query.
I did cure this problem myself, firstly I took the plunge and
removed the door card and peeled back part of the membrane. I did find that the shaft that links the outside door-key barrel to the inner door lock mechanism is a rattle-fit in it's hole in the mechanism (there may be a sleeve missing?). I put a piece of duct-tape around the shaft to stop any metallic rattle.
However, a test drive after re-assembly still produced a noise.
I remembered that soon after taking delivery of the car, I waxed it totally, including all the door shuts, and that when it rained, the noises stopped.
So I then used some silicon spray and cleaned around the door aperture, all the door rubbers, and the window guide channels. Hey presto, noise gone!
So please try the silicone spray first, before removing the door card!
If you need some tips on removing the door card, let me know.