As a current UK PhD student nearing the end of my three years, in my opinion you're looking for the wrong thing. Everyone will tell you that you need to be very passionate about your research and that it is the key to success. However, I don't feel that its true. The relationship between the student and supervisor is the most important aspect. If you don't have a good relationship, you will fail. So you should look for a supervisor that you can trust, who has the important qualities and skills (e.g. good communicator) and is willing to make time for you. You want a supervisor who is not happy with the way your current institution teaches its students, but instead is constantly evaluating him or herself to better the way they provide such an education. You don't want someone who will get lost in their own research, or is too busy as a Professor to see you often enough. I think the only way you will know who would work well with you is by comparing the lecturers who taught you for your undergraduate degree. Which ones were happy to provide assistance (e.g. timely, polite responses to your emails?) Which ones made the effort in lectures to aid your understanding by providing voice recordings of their lectures if you missed them, or mind-maps for each lecture, or turned up 15 minutes early if you had any problems? I chose this individual over a particular research topic. Obviously, the down side is that for three years I've been stuck researching artificial neural networks - which may or may not be my first choice. But I don't think I would be 3 months away from finishing if I was being supervised by any other member of staff in my department. Once you have the PhD, you are free to research what ever you like.