Breakfast
A 1.5kg bag of oats costs £1.50 in sainsburys. That is enough for 50 breakfasts (at 30g of oats each). I used to always use almond milk in my oats, but I ran out recently and was too lazy to go to the shop so I just used water and discovered it tastes exactly the same, so don't bother with milk for your oats. A 340g jar of honey in sainsburys is £1.40. Honey never goes off, mix a spoon of honey in with your oats to sweeten them and then top with a banana (usually around 16-18p each depending on where you go). The jar of honey will probably last you 3 weeks-a month depending on how much of it you use. That means that for roughly 7 weeks worth of breakfasts, you only spend around £12.80. That's just a little over £1.80 per week for 7 meals.
Lunch
Prepare your lunch and take it to uni with you rather than buying lunch on campus. Some of my favourite make ahead lunches are leftover stir fry (surprisingly delicious cold the next day), mexican rice and tomatoey tuna pasta. All of these are really cheap to make, I can send you recipes and price breakdowns for these if you want? Sandwiches are also quick and pretty cheap. A good tip for buying bread is to freeze it in sandwich bags, 2 slices per bag. This means that you don't have to eat a whole loaf of bread yourself within the space of a couple of days, and the leftovers won't go off.
Dinner
The lunch meals can obviously be used for dinner too, but I also like to make a big batch of soup so that I can just heat it up and have a hot meal as soon as I'm home from a long day, without having to actually cook. Carrot & sweet potato soup costs around 42p per portion to make and keeps in the fridge for about 3 days or can be frozen. Baked potatoes are good options too, with whatever toppings you like. I'm also a sucker for chicken/fish and vegetables. Really easy to make and really cheap.
I have loads of cheap recipes because I tried to see how much I could save on food whilst still eating relatively healthily a couple of years ago. Obviously I don't always eat simple, cheap recipes, but it's always good to have a list of cheap recipes you can fall back on when you want to save a bit of extra money.
One tip is to get your parents to help you stock up on long-lasting essentials before you go. If your kitchen is short on space, I recommend buying a box you can keep in your room to keep dried herbs/spices in. Get salt, pepper, paprika, cumin, basil, coriander and garlic puree and you're pretty much good to go for adding flavour to your food without costing an arm and a leg. Asda sell herbs and spices for around 70p each, rather than buying the branded ones for almost £2.