I did my Masters at Sussex at IDS and loved it. I am now looking to pursue a PhD. Even though I loved Sussex and think it is an ideal place to do a PhD there is no funding. I decided not even to bother applying. The PhD students there and at IDS spend most of their time trying to get funding. It hurts their research.
Ultimately, you should not pay for a PhD. You want to go to a school that is going to support you, even with money. It adds credibility to your research.
I would always go where the funding is. This way you can actually get through your PhD in 3 years. Besides its only 3 years and Germany is not so far away from the UK with cheap flights (with the money you could use to visit the gf and its much cheaper to live in Germany than Brighton). I think you and your gf can afford to be apart for a little while. no? I am in a similar situation now so it is a tough one to make, but if you are both in Europe, its an easier one. Also the 'reputation' of the department and university matter, but only so far.
Good luck!