If you are not going left (at the next exit) then you should not be indicating left
If you are not going beyond directly ahead then you should not be indicating right
Therefore if you are going directly ahead then you should not indicate until it is time to indicate left
As linked above rules 184 & 186 cover the use of indicators
In rule 184 “you should give an appropriate signal” and “Time your signals so as not to confuse other road users”
Note that no part of rules 184 and 186 have a “must”
which relates to the law. I was taught that the only must was to indicate left for the appropriate exit
This fits in with the original post
A very key point in the rules is to use the appropriate lanes, which default to left for turning left, right for joint beyond the half way mark and “whichever is appropriate” for anything else
There are many roundabouts that differ from the “normal” of a simple roundabout
Locally we have a few roundabouts that have signs to use all lanes if turning right (because of the volume of traffic that goes to the right)
That means traffic in the left lane could be going left, (including two left exits) ahead, right, potentially to a 5th exit after the right and also could be going all of the way back
If turning 90 degree left you should not indicate left on approach. So there are two exits where you should not indicate on approach, but use the left lane and wait to indicate before the exit