What does everybody do to sort these out? I have a few appearing on my rear door 

Methods, opinions on what is best and advice all appreciated,

TIA Louis

I have the same problem with rust pinhead spots just starting to appear on one rear door just below the weather seal strip. Unfortunately it appears to rust from the inside meaning you would need to replace the outer door skin to do the job properly. Anything less and it would simply reappear very quickly. Very annoying as the car is otherwise immaculate. The alternative would be to try and obtain a second hand door in the same colour not afflicted with the same problem. It appears the doors on the latter facelifts are not galvanised either so they will presumably suffer the same fate in due course. Pity GM cant make its coachwork as robust as the Volkswagen Passat.