2 lanes on a roundabout

[mondeomk4]

A roundabout near me has been redesigned and now on the approach road it divides into there are 2 lanes marked left/straight ahead and right.

The roundabout itself is quite awkwardly designed as it is fairly small with two narrow lanes marked.

To confuse it more the road that I would be turning right into has two lanes including a left hand turn shorty afterwards.

Twice in the last 2 weeks I used the right hand lane to turn right but someone behind moved in the left hand lane to undertake me on the roundabout. I think in both cases the drivers expected me to take the right hand lane on the exit onto the short dual carriageway.

Is is then wrong for me to move into the left hand lane off the roundabout if that driver is close behind me.

What lane should I use if I want to turn left off the next road?

It seems to have become accepted to use the left hand lane from the approach road to do this though it is marked to turn left or straight ahead.

Edited by mondeomk4 on Thursday 6th April 21:11

[mondeomk4]

Well it's just arrows on the road I guess it is normal practice and not something to worry too much about, if it happens a lot, it's just I wouldn't normally undertake on a roundabout onto a dual carriageway when it's not a traffic jam, I do have a long car.