I think I will probably stay the course and try and get a PhD. I went out over the weekend and chatted to some friends, and also explored the area where I live, generally doing something different than thinking about my project.
Reading the posts on this site indicates that there will be periods where I am not feeling very confident about my project and other times when I am enjoying it.
I think the moral of this, for anybody else, is to just stick with it. It will be worth it in the end!.