If it were me I'd be pursuing the point raised on the thread about AUC requirements regarding tyres BUT.....
Don't get too het up about the whole thing because you've learned a valuable lesson.....this is NOT picking holes in the way you handled it but just as a pointer to others who might face the same issues.
1. I hear what you say about it raining etc.., but from what you say it was the front tyres that were the issue as regards excessive wear....turning the steering wheel would have allowed a full inspection in seconds? A good lesson in what not to do when you take delivery of a second hand car. Did you not get the opportunity to give it a good look over when you tested and paid for it?
2. Why did you take the car to a 'dealer' (what sort?) for a tyre problem? Surely you'd go to a tyre depot and, once you'd established the issues, you leave the tyres on and drive back to the supplying dealer surely? Call me naive but not only have you allowed this 'dealer', whoever they are, to replace two very expensive tyres because
they didn't think they were up to scratch, but you've denied the supplying dealer the opportunity to inspect them. And for all they know, during that three weeks/1600 miles you could have been on any number of track days or other 'outings' and simply run the tyres ragged .... how are they to know otherwise?
But anyway, lifes too short, you've got four decent tyres now, so just go and enjoy the car and forget about it.