I am allergic to drivers sneaking past me on the left so tend to occupy the left lane if I can for as long as I need it. In any case, it is best to mirror-and-shoulder-check left on exit to make sure it isn't happening.

Where the Dorchester-Weymouth road crosses the Dorchester by-pass, with the football ground on your right, there are dedicated lanes (i.e. with arrows) for left, ahead and right but you find only one lane on leaving. Take the centre lane to go ahead and you sometimes have to fight with drivers on your left and right aiming for the same single exit lane.

As a former PCV driver I always found the primary gripe with roundabouts, as with driving in general, is the inability of some people to approach a situation involving a large vehicle and react in a sensible way. The main concern of most motorists is simply "how quickly can I get past this big slow lump of metal that is selfishly occupying my road..." and if they judge - wrongly - that the best time to do it is mid-manoeuvre then so be it! Anything as long as a bus or lorry obviously needs more roadspace when you turn, if you're negotiating a fairly tight r'bout with two lanes then you may well need to occupy both to avoid driving over the middle. But the whole process is made much more tedious by constantly having to anticipate some pratt coming steaming up the inside as the front of your vehicle swings round, no matter how obvious you make the situation by taking it wide. I also used to get frustrated when you'd stop in a queue of traffic, miles from the kerb and with no indicators going, and observe the person behind you pull out and drive down the outside, assuming automatically that any stationary bus is clearly at a bus stop. I mean, why else would you come to a halt?! People failing to indicate on r'bouts, or going three quarters of the way round it and then indicating as they start to leave, is my pet hate tho! Maybe they don't point it out anymore that on a r'bout you're always giving a signal, indicator or not!