As a driver, other drivers completely failing to understand any roundabout indicating rules does my fucking nut in.

It isnt that hard, there are literally like 3 rules to know indicating during a roundabout:

1. indicate if taking first exit.
2. If its a standard 4-exit round about and you are going straight, you only have to indcate as you exit.
3. Indicate in direction of roundabout if you are passing more than one exit, then after passing the penultimate exit before you plan to leave the round about, change from indicating with the roundabout to indicating your going to exit the roundabout.