My current pet hate is when you've spent almost an hour or more on cruise doing the national limit and are busy overtaking (having first checked that there's a sufficiently BIG and safe gap) only to find someone attempting to break the landspeed record, in usually the most inappropriate vehicle (like a 4x4, or these pickups that seem to be increasingly popular), charges up behind you flashing, honking, waving their arms (often both, just make sure they're well and truly out of control of their vehicle).
I can understand, to some degree, people getting a bit miffed with people sitting in the outside lane and doing less than the national limit when they really have no need to be there - ie they're not overtaking! But to almost ram you off the road because they apparently didn't understand that 70 means 70, not 100+ mph seems just crazy.
That and speeding in roadworks. I still don't get that. Even if the roadworks appear deserted - 40mph (or whatever they've set it to) means 40mph. God help the poor guy who just gets wiped out doing their job. Wonder if they get danger money!?
I drove in Germany for a year, and they seemed to have a different attitude. Their roadworks were really short sections (so no going for miles before you actually see men doing work, and you were free to retrun to normal speed just after the works) but everyone seemed to respect the fact they were working there, and doing what was a pretty damn hazardous job.