All bikers, 50cc or 1000>cc are entitled to their section of road space... the safest position being 2/3 out from the kerb as instructed by rider training.
The motorcyclist should be treated as any 4 wheel vehicle on the road, so if the need calls to overtake, then assume it's another car/van/lorry and use the other carriage way to overtake when safe to do so :winky:
I know you'll always get the odd maniac kids on their scooters crawling all over you through towns etc, sitting up your a**e rev, rev, rev, cutting in front, racing you from the lights... but these are the inexperienced spotty oiks that mummy & daddy bought a scooter for on their 16th Birthday, who then think they're king of the road