This is what it says on their website:
"Your UKCAT scores will be considered in our selection for interview. They will not be the sole indicator for selection. They will be balanced against achievement in other areas, in particular your academic performance to date. All indicators will be considered together in deciding who will be selected for interview. It is therefore important to understand that there is no universal 'cut off' score for the UKCAT when applying for 2009 entry. For example, if an applicant has an excellent academic background then the test scores will play a less significant part in selection. For those with weaker academic backgrounds (relative to our overall applicant pool), the scores will become more important. An applicant who may not normally be considered on academic grounds could be invited to interview on the strength of strong UKCAT scores that may indicate potential. Also, if applicants are very similar in all other ways, the score may be the determining factor in selection for interview.
Therefore, those invited to interview could offer a broad range of UKCAT scores. For 2008 entry, the lowest average score for an applicant invited to interview was 513 and the highest 776"