I heard Durham University's Religion Department is TOP. Watch
Durham's pretty good in that they don't really care about GCSE results. Obviously, your A-levels (or equivalent) matter when applying for undergraduate positions. They generally ask for a 1st class degree or high upper class 2nd for their PhD programs with a suitable masters too. From my interactions with PhD students and their experiences with applying, it appears that the most important thing to have when applying is a bit of passion and personality rather than just being able to point at a piece of paper and claim "I got this many marks". I think having interesting ideas and showing a little initiative will get you further than just having a high GPA. Hope this helps.