My biggest pet hate is the duelling lorries, where one goes to overtake as it can do 0.5mph faster. naturally it takes 10 miles to overtake, and just before it does- there's an incline and the inner lorry can catch up..
Oh, and of course they will just signal and pull out at the same time with no warning whether there is a car there or not. Really used to **** me off when I was bombing along at 70 with NOTHING behind me, yet the cock-holsters can't wait for me to pass first- they simply must pull out in front of me forcing me to slam on the anchors and sit there for miles while they 'overtake'.