So now I am wondering, with this talk of other vehicles
Did OP speed as much as they did just prior to the junction to get round some/one vehicle (maybe the van).
Which caused him to have to cut across sharply.
Maybe checking his mirror afterwards coincided with the audi breaking braking and hence his panic
Simply whatever the cause the OP was driving far too fast that closely to a junction he wanted to exit from. Get into the correct lane earlier and your driving will feel far less of an issue. Sure some ignorant douches will come hammering down the faster lane(s) and get in front of you.
Just consider that their dangerous driving will eventually lead to many of them having something like a head on with a barrier at some point as they have messed up and their driving isnt as good as their ego believes.
If someone is driving like a dick get away from them, its usually simpler to just slow down for a short period, let them get a little ahead and then speed back up, you can keep an eye on them to avoid them causing you more issues. Hell you can even send webcam footage to the police if you can send a decent amount, so they can deal with it if the person is in the wrong. Its almost always better to use less speed not more.