How universities use ucat for undergraduates ?

I think the way that UCAT is used vary from uni to uni, however, the score generally is used as a cut-off for deciding which applicants to invite for interview or alongside other factors like GCSEs and personal statement. Student intake is also different for each uni, but generally it looks like it's around 70-ish for most schools.

https://www.westholmeschool.com/wp-content/uploads/2018/11/Dental-School-entry-requirements-2019.pdf

This kinda gives a brief overview for all the unis, but I think your best bet would be to see which 4 unis you like the most and then see their specific entry requirements directly from their websites. Good luck!!