Ethics/legality of lane straddling when approaching r'abouts

OK it’s been 14 years since I got behind the wheel of a truck but these roundabouts with 2 lanes on the approach and only one lane around the roundabout really do annoy me, they are just crazy! I always stick to the nearside lane if I am going straight on (Or turning Left) but often get some idiot in the outside lane thinks he is going to overtake me on the roundabout even when there is not a lane to go in. I blame the road planners for designing such idiotic road layouts!