Go for it if you want. But remember you are not guaranteed anything, even if you think you are suitable (and you may well be). The admissions tutors arn't infallible. Every year people get get in who deserve a place, and people get in over others who were perhaps better suited for the course. If you think it is worth the gamble, remembering that tuition fees increase next year, then by all means go for it. Your GCSE's don't look pretty mind you, and if they need to decide between similar candidates based on tests/interview performance, you will get the short straw because of them. I would happily hazard a guess that the top 8 GCSE's of students at cambridge averages above 4A* and 4A's.
Think carefully about the reason you want so badly to go to Oxbridge. Do you want to go because of the prestige? Do you feel that without a Oxbridge degree your life will not be perfect, and that there is no other route in life? These are the wrong reasons, imo, for applying there. You should put it relatively. Harvard, MIT, Caltech and other US unis are probably better that Oxbridge. Don't you want to go to one of those now?
Some good reasons for wanting to go are; the college system, the amazing scenary, the tutorial teaching etc. If this is why you actually have your heart set on Oxbridge, then go for it.