Thanks to Akira, Fons, Gunther and Simone for posting here - all gratefully received.
Gunther - I do work almost entirely from instinct but a) I've been doing it for a long, long time*, and b) I change my gear, especially camera-bodies as seldom as possible. In this way I learn to know pretty well what they do, and I can trust them and no longer have to wonder about technical things.
* Too long to mention. but to quote the fashion photographer, David Bailey, "in photography everything is so ordinary. it takes a long time to learn to see the extraordinary."