I still remember when I came to study in the UK. I was expecting most things that I saw once I got to Uni, mostly because they sent me a welcome pack, and they also had a nice video that covered all the bases. There's a few things they did not (could not?) tell me, so I'll try to fill in some gaps I had when I landed.
1. Know your chains: the first thing you should familiarise with is the many food and supermarket chains that can be found in the UK. Some you might have in your country, others you don't. Look up the menus online, see what the prices are, and what kind of food you fancy (sushi? grilled chicken?), and which are close to you. Then repeat for supermarkets.
2. Cook local: Britons might not share your passion for a specific food, or find it exotic and thus make it quite expensive. I'd suggest checking some British cooking websites to see what you can make with supermarket ingredients. BBC GoodFood is a personal favourite, Christians Against Poverty also has some budget recipes if you want to save. Pro tip: check your fridge size before shopping, and make sure you have time to cook the things you're buying.
3. Check the socials: from what campus restaurants to avoid, to the University's unofficial mascot, you can learn a lot from your University's Facebook group. You might even meet your classmates beforehand, and score some pretty nice deals on used textbooks.
4. Buy online: whether you are busy, you don't have a car or you'd rather not go out in the British rain, buying online for trustworthy websites might save you money and time. Don't stick to big international names, see who sells what in the UK, and remember to keep your postcode handy. Supermarkets do also sell online, but they might substitute something they are not currently stocking with something else, so make sure you know what their policy is.
5. Enjoy: you have a potentially great time ahead of you, so make the most of it! It doesn't have to be clubbing or sports, you might find your university has all sorts of interesting student-led activities, from your local SCM group to medieval fencing or first aid; and it's going to look super on your CV!
That's my advice, now don't forget to ask around!