It's a little late to go through UCAS, so email the unis and just say "hi, my name is [X], but my UCAS application says my name is [Y]. Here's proof of identification, and here's what actually happened." Are your unis far away or nearby, because you might actually have to go in person to show them your ID & certificate of name change (assuming the problem is that you changed your name officially after sending, and not that it's a typo, but if it is a typo, same thing should apply).