The northern-eastern bit of West Sussex. I think it is a rural, sub- and intra-urban thing.
The A281 south of Horsham, where most conflict occurs, is a 'special' road, ridden and driven on by 'special' people. Cyclists, especially peak hour cyclists, are a relative rarity. Cyclists who hold secondary rather than gutter hug, or, God forbid, takes primary when the need arises , rarer still.
I used to think it was me and the way I ride. But I've too many colleagues who cycle to/from work (inc. one who uses an almost identical route to me) who experience the same as me, or worse - I've never had a MaccyD milkshake thrown at me on a commute, week in week out to feel that way any more.
I could change my route, and go where the hills have chevrons, but I prefer to ride in one way and home another. And I don't see why I, or anyone else, should be bullied off a particular road but a knuckle-dragging loft insulation operative in a defective vehicle.