As far I am aware, there is only one interview. So everyone will fill out the same application on ORIEL and then get invited to an assessment centre. The assessment centres are scattered around the UK so people just pick which ever is most convenient and go there, has nothing to do with the hospitals they are applying for. The assessment centre has a calculation test, a situational judgement test and 6 multi-mini interview stations. After assesment, people will be scored and then given a unique rank. Then offers will start to be given out. You only get one offer and once you accept that, your information gets passed onto the hospital. So, the hospital may choose to check references after you've chosen to accept the offer. So there's only one interview and it has nothing to do with the hospital. It's a bit of a gamble really considering the hospital has no say in who they get given for pre-reg as they have nothing to do with the interview process.
It also doesn't matter where you went to uni. The whole process is based on how you perform at interview, and it's not like they're going to give someone more points just because they went to a certain university. I've also had interviews before for placements and stuff and they really didn't care that I go to one of the top ranked pharmacy schools in the UK. The only time they slightly cared was if they went to the same university, just because they could ask about lecturers and stuff.