If you're applying to a quant role, then it'd be an issue. Consultancies look for more of a balance of quantitative and soft skills though - social sciences (economics, management sciences, etc.) have a pretty close match to the consulting skillset. If you're applying to a general grad role then it wouldn't be a problem most places - after all, English BA's are welcome and there's more statistical analysis in social sciences. Age shouldn't be an issue, and there are plenty of places that will appreciate having someone with a bit of "grey hair" to give at least superficial credibility in front of clients. Best to stress your willingness to start at the bottom, learn quickly, and prove your ability on the job, to quell any concerns about your age.