Not to be funny hon, but with those grades, don't you think it would be best to drop the U? Or at least drop one subject you least preferred because statistically, the chances of you getting good grades at A2 is incredibly slim. Will your school/college even allow you to carry on doing 4 subjects?
No one can tell you what grade you'll get next year love. You need to be realistic on your options and figure out what can you do in order to improve your grades and possibly work ethic to get more of a higher standard patter (ACDU is quite a sporadic set of results).
I would advise you to drop the subject you got a U in and retake the exams where you achieved low grades. If you work your socks off, you can achieve three A's. Just priorities your time well.