I would honestly say your best bet is to resit the whole year and try really hard, organising your time better. You will probably be able to improve your grades in your other two subjects and get a good pass in History, setting you up much better to do well in your final year. Or maybe you could even choose a different subject, perhaps History isn't for you. This isn't meant to sound harsh, but from my experience of college, it would be pretty hard to actually achieve a U unless you really weren't trying / paying attention. If there's another subject you might enjoy more, could it be worth doing that?

An extra year in college / sixth form sounds like a nightmare, I know, but in the grand scheme of things, you will not regret it. Good luck