The roundabout sign
The roundabout sign means Slow Down, prepare to Give Way and if necessary stop to avoid a collision.
So, as you're approaching a roundabout, you must get into the correct lane, indicate if turning, and give way to traffic already on the roundabout.
Enter the roundabout when there is a safe gap in the traffic.
Giving way
Slow down as you approach a roundabout. You must give way to traffic already on the roundabout if there is a risk of collision. Enter the roundabout when there is a safe gap in the traffic.
Indicating
When approaching a roundabout, if you are turning left or right, you must indicate left or right.
When exiting a roundabout, whether you are turning left, right or even going straight ahead, you must always indicate a left turn just before you exit, unless it is not practical to do so.
Single lane roundabouts
The rules for slowing down, giving way and indicating when approaching and exiting at roundabouts are the same for single lane and multi-lane roundabouts.
Cyclists and roundabouts
At roundabouts with two or more marked lanes or lines of traffic, a cyclist has the option of turning right by entering the roundabout from either left or right lanes. However, if the cyclist chooses to enter from the left lane, the cyclist must take care to give way to any vehicle leaving the roundabout.