My understanding of roundabouts is based on how many junctions you have on the roundabout as well as the 12 o'clock rule.
i.e. if the roundabout has only three exits and your exit is number 3 and it is straight on in effect, you should still be in the right hand lane even if it is at almost 12....
Likewise if your on a roundabout which has say five junctions and only one of them is beyond 12 O'clock, you need to be in the right hand lane for numbers 4 and 5....
It should also be noted that traffic in the right hand lane, if indicating to turn off at a junction has right of way, as it is illegal to undertake... therefore where you hit them Nobber is very important, i.e. if they hit your drivers door, they are in the wrong, but if you hit their front passenger door etc, your in the wrong.... If either of you hit front wings it will be either knock for knock or you need witnesses, and if the witnesses say you speeded up to push past, your in trouble.
As Cannonball says, the easiest method is high speed, and go straight over, everyone gets out of your way, esp if you lean out the window and shout, "my brakes have gone!!!"