I am an Englishman doing a PhD in Germany. However, due to time problems beyond my control the project was agreed by everyone to be no longer possible. This happened one year in. Six months later I find myself with no interest in my 'emergency' project and a supervisor who's difficult to work with (this has been a concern throughout). I'm very unhappy and want to leave and take a completely new direction as I have no interest in pursuing a career in my PhD subject. How badly will this affect my future chances of a PhD/job?

be extremely determined and speak to your supervisor about it. Also consider changing supervisors.