Necessities:

• A laundry bag – most halls have some kind of laundry room (University College Birmingham uses circuit laundry) and trust me, doing your washing without a big bag is impossible.
• Batteries – something most people don’t think of, including myself. But I needed them two weeks into uni!
• A bedside table – most halls don’t provide a bedside table and if you’re like me, you’ll want a place to put a lamp, your phone and a drink! I just went to Homebase and picked up a small one for £20.
• Antibacterial wipes – Wilko sell really cheap antibac wipes which are perfect for cleaning surfaces and even your toilet! They make cleaning so much quicker and easier.
• Coat hangers – may seem obvious but forgotten by many!
• Decor – photographs, fairy lights or a cool lamp. Uni will feel much more homely if you decorate your room a little. 
• 16-25 Railcard – if you’re going to be travelling on the train a lot, a railcard is great. 30% off all train journeys!
• Full length mirror – this one may seem a bit extra but if you’re like me and like a full length mirror then bring one because most uni rooms don’t have one.
• A year planner – I bought one for the wall and stuck it to my pin board. It was about £5 off Amazon. You’re suddenly going to have a lot of plans and a lot of deadlines, so I really recommend this.
• Extension leads – buy like four because there are never enough plug sockets!
• Clothes horse – don’t bother with tumble dryers because they are expensive and rubbish!
• Microwavable bowls – the microwave will be your new best friend.

Of course there are way more things you need, but this is some stuff I forgot and had to buy after I had moved in.