Cyclists riding side by side are easier to overtake than when they ride one in front of the other, as your TED is halved. You give a cyclist as much space as you would a car anyway, so really it makes no difference. If the road isn't wide enough to overtake a car on, then I would agree that common sense would dictate that the cyclists do drop back into single file to let you pass, but again you have to think about whether the overtake is safe to carry out if the road is that narrow.
Well if there are parked cars on either side and on coming traffic, it makes it a tad difficult.
They'll be there talking to each other as they casually trundle along completely remorseless of the 760 mike tailback they're causing.