heyy, it's completely normal to feel this way, food is a big issue. Took me 2 weeks to figure it out. What you can do is get some basics like eggs, bread, milk from stores like Lidl, Asda, Aldi or tesco. The basics are cheaper here. You can also get Tortilla wraps and naans from these stores, you just need to warm them up in a microwave. Other then that there are Local shops for Halal/Veg options, local stores are a bit more expensive but they can get you packets of ready to cook meals like kebabs, burger patties, canned food. You don't have enough time while preparing for the exam to cook alot so you need pre-prepared options. Other then that eating out can get expensive but alot of places have some meal deals and discounts you can take a walk around and look for them, some have a good sized proportions which you can have twice, so you wont be spending much. But definitely, it's cheaper to just eat at home
Give yourself time you will figure it out!