For clarification this was not a crossroads, but a T-junction. I had two options, to carry on along the road or to turn right.
I didn't turn before the centre line of the road I was turning into.
It was my 'right of way' in the sense that whichever of those options I chose, the motorist was required to wait (give way) before joining the road I was on. I'm not convinced it advances the understanding of the substantive point to split a hair lengthways about the language chosen.
I want to be quite clear about this. There is no question but that the motorist pulled out before it was safe to do so and was at fault. My post was not about that, but about whether I should report it.
I did call the police, explained the situation, and was told that I could report it if I wanted to but no action would be taken without video footage or a witness. They were sympathetic to my view that there is a broader principle at work here, however still couldn't help.
I spent some time mulling it over first however, hence the delay in providing an update.
On reflection, my first attempt to use this forum has been pretty unsatisfactory, so I thank those that have tried to be helpful, apologise for wasting the time of those people who have been snarky, and wish you all well.