Well it will be spectacularly unlikely for you to get an offer as they mostly prefer students who spend 2 years doing A levels and they have very high standards especially for maths (please dont be fooled with the fact that they want an A in maths for economics they just do it to attract more applicants on ucas 99% of their applicants get an A* offer) they are also extremely competitve for economics as i have known several people attending oxbridge who were rejected by warwick and half the guy there have econ offers from LSE or UCL this shows the calibre of their students!, im sorry for being blunt but it's true.
But that doesnt mean you shouldn't give it a go make sure your personal statement is ace and you never know, i know a guy who got AAB and got into warwick for economics but that was in 2009.
Anyway goodluck!