From my own personal experience, I simply googled to see what universities were offering Journalism as a course. Some of these universities also do courses like Multimedia Journalism, Fashion Journalism, Sports Journalism etc. So be sure to have a quick check on each of these universities. From there, see what sort of modules each of the different courses offer. This will give you a good feel for what sort of stuff you can expect, and will also help you decide if you want to do a more specialist Journalism course or not.
Then have a look at the entry requirements for some of the courses you're considering. Do they specify specific subjects you must take or do they just want you to get a certain amount of UCAS points/grades?
Have a look at different universities as well. Look at the different courses they offer, and if it seems interesting, then look at other universities that offer it so you can get a broader feel for the subject. I've found that some universities will offer near identical courses, but one university will explain the module better than the other.
Look into the courses and see if you'd be genuinely interested in studying them, and that you're not just hoping to get into it for money, or because it sounds cool, or because you want to go to University. Like have a look at different subjects and see if anything sparks an interest. Even try searching on Youtube for different universities and watching videos on their courses.
It doesn't have to be something that you enjoy at A level, although, if you are obviously hating a subject a lot, then perhaps it'd be unwise to take it at university. As long as they don't mention you needing to have specific subjects that you don't have, then any course is fair game.
Do something you're genuinely interested in. It takes a lot of time to look through the different university courses and find something you like. But it'll be so worth it. Like you'll be spending years (and a lot of money!) on the course, so take plenty of time to look into your options. Try and attend open days, or taster courses in subjects that you're considering, or if you can't, then try looking up some of the career prospects etc. Is it something you'd be interested in doing as a job? etc