Original post by dendodgeChemistry isn't that important for a science degree. They often just ask for two science subjects, and I imagine economics would be included in that (maths usually is, anyway).
Your other subjects demonstrate a range of skills, so there's plenty you could do with them. Obviously, you won't get into chemistry, but I wouldn't be surprised if you could get onto a biology course (somewhere around the middle third of the league table, I expect) or something.
Of course, the three sciences aren't the only options. Based on your own interests, look at courses you think you'll enjoy. If the entry requirements don't specify chemistry, you'll be totally fine without it.
If you do want A2 chemistry, all you can do is ask your teachers nicely if they'll let you resit the AS and try to bump your grade up. If you do that, you'll probably need to do an extra year at college/sixth-form - while that isn't ideal, I can assure you from first-hand experience that it's not all that bad. I definitely feel much, much better-prepared for uni after three years than I did after two.
Good luck!