1. No idea.
2. Uni ID is fine.
3. Quite a long time - towards the end of term I think, although they like you to pay sooner. They'll give you time.
4. Depends on the hall. There'll be a microwave, but don't expect much else.
5. Don't bother buying any. There's one (fairly cheap) book of texts - extracts from Locke, Marx, Hume etc - that will be worth buying at some point, other than that, it's not really necessary to buy any, although you might wish to buy a couple at some point. Unlike some subjects where you just have one textbook, in politics you'll get a reading list with hundreds of things, but even the main books are not normally worth bothering purchasing. I would certainly delay any purchasing until some weeks into term, when you'll have more of an idea (and remember that the first year is only a qualifying year, so doesn't really count for all that much).