The OP has been very quiet,
and the only ones blaming the driver are the two kids on here.
Saw another kid ride up the inside of a left turning lorry this lunch. Lorry was indicating, I pulled up 2-3 cars behind, bloody student (on a quality cannondale) goes up inside, between lorry and railings. Fortunately the driver slammed on at the last minute. The student on a bike carried on.
I thought about having a word, but no point arguing with an idiot. Riding like that he won't last long.
Driver's don't always look in their mirrors, and aren't really looking for an idiot to come up inside them when indicating FACT. The words 'but the driver should have looked' when you are six feet under don't mean alot !
Stay safe and don't ride like a nobber.