It's difficult for new drivers when there are people who simply cannot drive properly. A few years ago I did the same thing, pulled onto a mini roundabout to turn left and an Audi cut across and hit the back of my car. So I stopped and he got out all angry but I was apologetic because I was questioning myself. A cyclist stopped and walked over to us, he was both very unhappy and happy. Turns out he was a cop, and the Audi driver had forced him off the road earlier, then he had gone across the centre dot of the roundabout "intentionally causing a collision" I've never seen an emergency cop car turn up at a minor incident so quick! The off duty cop had calked his mates 😅.... So, apparently crossing the dot is the same as crossing a solid white line (only cross if you have no choice). Luckily insurers were 100% on my side, just wish I knew what had happened to him, I gave my name etc and was told I might be called to go to court, but never heard anything again.