In my opinion a lot depends on how you approach this type of situation.
If you have not planned correctly, and come screaming up behind traffic lined up in lane 3 or 2, THEN move into the next left lane in order to overtake, you have committed the offence of overtaking on the left, which is driving without due care. You could then make it even worse for yourself if you accelerate hard passing the vehicles that are now on your offside, and pull abruptly back out into lane 2 or 3 in order to overtake a slow mover in the nearside lane.
However, if you look far enough ahead, and gradually move out of the (soon to be) busy outer lanes, then travel in lane 1 for a distance, slowly catching up the traffic in the other lanes and then overtake on the left, you have not 'moved to a nearside lane in order to overtake'. You are already in that lane prior to the hold up, and so can carefully and steadily overtake the numpties in the offside lanes. HOWEVER, if you are on your bike, be especially careful for your own safety. Drivers WILL start to change lanes and THEN check their mirrors; not good if you are close by them!
It's just my opinion, mind!!!man8um