I was at the GP surgery a few months ago, my GP popped his head out to tell me he was running 20 minutes or so late, and then he was called away to an emergency. It was about an hour before I saw him. I was just grateful that I wasn't the poor sod needing emergency treatment.
I know it can be frustrating waiting for so long, but you never know why your GP is running late. S/He may be breaking bad news, dealing with an emergency or just snowed under.
I would hold off on making any complaint. You will just know in future that appointments are usually running about half an hour behind and you will be prepared for it. Or ask for an early appointment, before the waiting time expands too much.
I think that we need to appreciate that the NHS is free (OK, we pay taxes, but still...).
If you want quicker service, go private.