Percentiles don't mean a massive amount. Someone I know was in a very low percentile (with not a great score) on the MSAT and got in this year at the first selection centre. Its not just about your UKCAT, it goes on a lot of things; work experience, degree, how much they like you at the selection centre. There will be cut offs but I don't think being below it automatically excludes you from being considered, especially not if you're close and the rest of your application is good.