I used to not use a bell, figuring that my cranking along through the rocks, roots, etc. created a noise akin to a threshing machine with a lot of loose parts would be enough to warn everyone within half a mile—-then the years passed, with my hearing gradually going the way of all those older hikers/strollers–so I, too, now have a bell and give a quick ring when approaching.
The old standby “bike on your left” or “bike on your right” can prove problematic as I am pretty sure some of those people either don’t know their left from their right—or they misinterpret and move left when you say “on your left”
+1 for bell and polite shout followed by thanks – Ride a lot on Peak family trails (with my Peak family!).
Biggest dangers are the bemused reaction as described (‘I heard a bell so I’d better act like a bollard’), walking pole gestures (‘Look at that wonderful scenery’ – gestures with extended walking pole across trail) and dogs, either loose or (worse) on those long extending leads