Two weeks for an appointment? My practice generally offers one on the same day if you ring in the morning. Or you could just turn up.
But as for the scans above: yes, they missed something in the second scan. But often you only see things if you know what you are looking for, and it might have been small at that stage (not visible on the first, you said)
The NHS is overstretched an underfunded as it is: taking the money & doctors out of the system to defend themselves is not likely to help anyone else, rather the reverse.