Agree with the above advice. Focus on your supercurriculars and make sure you prepare thoroughly for your entrance exam (MAT/STEP). It is very important that you take your entrance exam preparations seriously and devote significant attention to them, as putting in the same effort as you did at GCSE simply will not work. My advice is to try and cultivate an enjoyment of the type of problems on the exam papers, which should make it less of a battle against yourself to do past papers and the like.
But to answer the actual question, yes - as of now you have a competitive application. I will however emphasise the fact that all of this is meaningless if you don't perform in the admissions test. And vice versa, any weaknesses in your application will be ignored given a sufficiently good admission test result (at least for Oxford). Good luck.