Hi Androcles:
What a totally frustrating situation, I know, being one of no doubt many thousands to have "suffered" a similar fate.
The correct thing for you to do would be as you say at a).
However, don't laugh, in the event of a marked Police vehicle coming along, it is feasible that the driver at the head of the middle lane queue could be reported for what's called "inconsiderate driving", i.e. pootling along at a speed well below the maximum when there's an available empty lane on his nearside. In fairness, though, he would need to have been driving in such a manner for some miles and the Police would need to show that he'd had numerous opportunities to pull over but failed to do so.
Anyway, if you've now stopped laughing, we all know that the chances of finding that Police car are as rare as hens' teeth. So don't hold your breath.
But it's the sort of driving behaviour which winds us all up, isn't it?