Hi there
I can answer some of these, I don't do Maths, but hopefully some of what I say will be useful.
1. As far as I'm aware, at some point, you'll be given a reading list. Some books will be available at the library, (10-week loan length), other than that you can get them wherever you want (I like Abebooks.co.uk, it's fairly cheap).
2. There is a doctor on campus that you can register with. Since you're an international student I'm not sure how registering works I'm afraid.
3. Since each room has a lockable door, each room is classed as a separate residence, so will require a TV license if you plan on watching live TV. Most students don't get one.
4. The university does employ some students, and there are part time jobs available in town, As you're an international student you may have visa restrictions on how many hours a week you can work. You'll have to check on that depending on where you're from.
5. If you want I can find out what some maths students use as a laptop, but there are computer labs available for you to do coursework on. If you're wanting to take notes on a laptop you'll need something that can run word. Since I'm guessing you won't be wanting a Macbook you'd be looking to spend about £300-£400 on something that can run Word and PowerPoint. A decent amount of RAM and a good processor should be all you need. From there it's mostly about what will work for you.
Any questions let me know