Heyy, well I've got onto the Radiotherapy course, but I would think that the Radiography interview is quite similar. I think it will depend on who interviews you, but I got asked things like 'Why I want to do Radiotherapy?', 'What qualities do you think a Radiotherapist needs?' 'What skills do you think you can bring to the profession?' etc. I didn't have to have any test when I was at the interview
Make sure you are 100% sure you want to do radiography, and then if that is the case, make sure your personal statement is based all around Radiography and not other things, as this is their first impression of you and forms the basis of whether they want to invite you to the interview stages or not. Also if you do get an interview, just relax and be yourself. I found the interview quite relaxed and informal, and it was more of a general chat that anything which helped me personally.
As for preparing, I think just getting as much experience as you can, and reading up around the subject is good. Also make sure you go to the open days because there are normally current students their to talk to which is always good to find out the students perspective of the course, and not just the university's!
Good luck in your application, and if you wanna ask anything else then please do
xx