From what I have learnt during my time in Sixth Form College, your GCSEs mean very little to Universities - unless you are looking towards a lower-level university and haven't managed to meet their UCAS requirements.
I wanted to apply for Durham myself and had been concerned that having a couple of disappointing grades mixed in with my GCSE results would be an impediment towards getting offers. However, my English Literature tutor has informed me that they will do little more than skim over those results.
Honestly, with your predicted grades I would not be worried at all. You are performing well academically and as long as you pass with B's you will certainly be allowed to study your desired subjects at an AS/A2 level. Just make sure that you keep on top of your A-Levels, revise regularly, get ahead of the class over the summer and keep your attendance high. When submitting your application keep it interesting, clarified, unique, insightful and written with conviction - but your college/sixth form should assist you with that.
I know individuals who have applied for a 2016 start who have received conditional offers at Russell's Group Universities despite having as few as 6 GCSEs.
Do the best that you can but do not worry about your GCSE results being an obstruction for your future.
Good luck!