I indicate only when I judge that my change of direction will affect someone. Otherwise, I don't do it. On motorways, there's generally no point signalling to move back in if you've just overtaken someone. You're going faster than them so your move back in won't affect them. At roundabouts I signal if it isn't clear from my position that I'm turning right. There's little point in signalling to turn left, and signalling that you're leaving the roundabout can be confusing, unless it's at one of those great bit big horrible ones such as the one at Exeter services.