Dundee certainly used to select based on PS as well, as when i applied there i was rejected on the basis of not mentioning enough extra-curriculars.
Just had a look at the site and it says
"From 2013 cycle information on non-academic achievements and references will not be considered until interview. " So if that means this current cycle, then yes you probably should be interviewed if you have better grades and UKCAT than other interviewees. If it means the next cycle then perhaps it only just changed.
I don't think it would hurt to ring the admissions office and explain that you know of others getting interviews with lower scores and ask why you weren't called up.
EDIT: As for the GCSE question it says:
We consider the primary qualification (A levels, Highers, Degree class etc) and also the relevant previous stage (GCSE, Standard Grades, School exit exams etc. as appropriate).
So they are taken into account, which may be why you were rejected.