Simple -

Right lane - For turning right, going straight, turning left, or for parking and waiting for friend.

Middle lane - For turning right, going straight, turning left.

Left lane - For turning right, going straight, turning left.

The golden rule is the bigger the car, or if a pick up, then go in any direction that takes your fancy.

If you are worried or frightened by roundabouts always approach them whilst texting, this gives you carte blanche to enter the roundabout and all other users will stop for you.

Works for me