Someone slowed you down for a minute or 2 on your journey, Diddums.
Unfortunatly HGV's are restricted, there is some variance in the speeds as its done by pulse from the gearbag, but as with any other form of movement, if your going faster than the person infront you go for the overtake, the other wagon may pull better uphills, have a heavier load and have more gravity downhill, or the driver of the wagon in the inside could just be a complete flid and not think to let up the gas for 5 seconds to let the other go past and free up the lane,
But at the end of the day, we just want to get to our destination and sometimes get home too,
All I can end on is that you should just deal with it, its not the end of the world, or will it cause the end of the world, You need HGV's more than they need you.
HTH
G