Aww thanks
Congratulations on your GCSE's by the way
In terms of advice I would say in terms of applying I would,
- Try and read around your subject with particular emphasis on stuff that you find interesting e.g. books/ etc which can be useful in a personal statement or in interview. Try to do this mainly in year 12 when you have more time as trying to cram at the beginning of year 13 could be difficult.
- Make sure you research thoroughly which college you want to go to as they can vary significantly in what they offer e.g. facilities/ entrance tests/ en-suite etc. Also, make sure Oxford is for you as in reality it will probably be intense.
- In terms of below average GCSE's I would firstly say, don't let anyone on the TSR tell you that you are ultimately not good enough as it can be quite daunting when you see people on here with 200+ A*s. They may not be the highest but that doesn't mean it's all over. Secondly, I would really try and nail your AS's to get solid predicted grades/ nail any entry tests/ personal statement to really let your passion for history shine through (although try not to use the word passionate :P) and to solidify your chances as unfortunately some may have higher GCSE grades.
Finally I think the best piece of advice I can give is to try not to see Oxford as the be all and end all (although still be really passionate) I know this sounds rich coming from me but trust me, just because you don't get in (although I'm sure you would) doesn't mean you are stupid/ going to fail in life. It's the students that make the uni, not the other way round and I truly believe that a motivated and enthusiastic student would prosper wherever they went (wow, this is getting deep :P)
I hope this helped and feel free to ask any more questions about applying/ interview etc. Good luck