Firstly: shopping. It's a good idea to make a list before you go that you stick to so that you can stay within your budget and don't impulse buy. And before you go, try to find which is the best value supermarket in your area; mySupermarket is an online grocery price comparison website to see which shops in the UK have the best deals. If you shop in places like Tesco, Sainsbury's and Asda it's generally cheaper to buy the store's own brands since the products are normally sourced from the same places as the expensive brands. If you are sharing your flat, get together with your flatmates to have a kitty for rice and pasta that you can buy in bulk and share.
Finally a few ideas for storing food. Keep raw meat, poultry and fish at the bottom of the fridge so they don't drip onto anything and make sure you keep raw and cooked meat separate from each other. If you're storing leftovers in the fridge, make sure they cool down out of the fridge first so you don't compromise the temperature in the fridge. And one finally useful tip: open tins upside down so the contents don't stick in the bottom of the tin!