I know some people who skipped GCSEs and went straight to a level and are now at (a British) university. Depends on the course, check the prospectus and phone the university admissions office for advice.
If it is the uni of california (UCLA) you want to apply to here is its info on international students (I'm assuming you will be if you are thinking of a levels/ GCSEs)
UCLA Undergraduate Admissions and Relations with Schools: International Students
Seriously though, if you are considering this you should do some of your own leg work, and improve your written English - or you will find yourself disappointed.