When I learned to drive the rule was:
If turning first left off the roundabout indicate left, stay in nearside lane and execute the turn.
If going straight on do not indicate on the approach to the roundabout, indicate left as you passed the first exit and leave at next exit.
If taking third or even fourth exit then indicate right, move to the right, circle roundabout in the "inside" lane and indicate left as you passed the exit before the one you wanted to leave by. Move into the "outside lane and exit roundabout.
All seemed simple enough to me but the THW when taking driving lessons was told this is no longer correct. She carried on doing what I had told her and still passed ~ she never came up with a satisfactory explanation from her instructor as to where I was going wrong.
I am no wiser.
PS I should add that if the roundabout is "laned" either on approach or on the roundabout itself then get in the correct lane ~ all else is as above ..... mind you there were very few roundabouts when I started driving ~ many more junctions with traffic lights but similar movements to correct lane and indications still applied.