If there are 2 lanes in and 2 lanes out at 12O'clock, then you can be in either lane, as long as you exit at 12 o'clock in the same lane.
Don't think this is in the rules of the road, but seems to be common practice when the 6 o clock to 12 O'clock route is the "main road".
Problems I experience with this though.
- if you're on the inside lane & your outside lane "roundabout partner" enter the roundabout together, you need to watch that they don't decide to exit on the (your) inside lane.
- if you're on the outside lane, you're inside lane round about partner could be going for the 3 o'clock exit (some people always take the inside lane no matter what).
- if you're on the outside lane, with no roundabout partner, someone entering at 9 O'clock could assume you're exiting at 3 O'clock and not realise you're about to cut across him.
My god, it's a jungle!