Go to your GP and ask for Duac gel - it contains both benzoyl peroxide and clindamycin. Otherwise you can get clindamycin prescribed on its own. Or you could try antibiotics - I take tetracycline which doesn't completely get rid of acne, but it fights off the bacteria that causes acne and leaves your skin in a fairly manageable state.
If you're a girl, try to avoid dairy products for a week or so, and see if this helps. Androgen hormones in cow milk can affect your own hormones and aggravate acne. However, this isn't the case for everyone, so just try it for a few days and see if it works.