This is what happens when you get so many articles and posts regarding a subject that you lose track of which one is which and where you found it.
I did indeed follow your link Bob and then forgot I'd read it the next time i needed it . The grey cells aren't what they used to be but in fairness they have been working away for the last 75 years and I'm hoping they'll not let me down too badly for the next 25...I can but wish!

Ok, I've now gone back to the JefL article, very good and I'll definitely have a go at what you suggest re the safety spring. I'm not using my safety at all as it seems to be the basis for the firing pin dropping out ie the void behind it.
Thanks again Bob and to JefL and the others who contributed to an excellent guide.
Jim