Applying to University with bad predictions

Hey guys
I’ve had a rough 2017 and I’m currently in my seconds year of sixth form. My predictions are

Economics - A
History - B
Maths - C

I don’t believe these predictions do me justice and have tried to get them changed by my teachers but they won’t budge. No one has ever even gotten an A in my sixth form for history before which led to me getting my own tutor.

Is it worth going through clearing but the only thing I worry about is I want to go to a Russel group and study accounting and finance but will clearing with worth it. I think I can get AAA and I have the determination and drive now that I didn’t have in 2017. I’m just really worried and think these predictions don’t do me justice. Is there anyway to approach this situation as I don’t want to take a gap year.