They make their entry requirements clear..and at the interview stage they can find out who they believe will make good doctors...not everyone who gets an interview will get an offer..they also do have a very large medical school and can therefore give out many more offers in comparison to some of the other medical schools...yes, one of the main factors in inviting people for interview is gcses...but they do not use the ukcat..and some universities use the ukcat significantly (by having cut offs etc), so you could argue how can you use the ukcat to decide who to invite for interview, when it is a fairly new exam with little evidence...Just like some unis use the ukcat to narrow down candidates, birmingham use gcses