Hi
I'm just finishing my first year so I'll answer your questions as well as I can
1) I spend around £20-25 a week on food, for 7 dinners, 7 lunches, breakfast, milk, bottled water and snacks. But I know people who survive on a lot less, and eople who spend a lot more. Going out off campus I spend around £20 because taxi fares aren't cheap, entry is around a fiver and then drinks. Going out on campus is obviously much cheaper in first year, I tend to only take £5-10 out in the union. They're my two core costs and then buses are around £1.70-2.35 single if you plan on going off campus a lot. then factor in train fares home or to visit friends, and then stuff like if you plan on going for a drink in an evening or something. I budget about £60 a week but some of that usually goes on things like a coffee or extra treats from costcutter.
2) I know people in arthur vick who are definitely up for going out and they're kitchens seem like it as well. But, I live in Jack Martin and I wrote basically that on my personal statement as did the rest of my corridor, we all meant it differently and all have completely different lifestyles which can cause conflict from time to time so be really really specific about how much you want to go out, how much noise you could deal with, etc
3) Rootes seem like fairly welcoming people, everyone I've met from Rootes are lovely but can't say I've ever been out with them as most of my friends live elsewhere on campus. I can't see anyone minding you wanting to go out with them, every time I've been to other kitchens on campus no one really minds.
4) the other halls that are not apartment style are cryfield and westwood. I've not met anyone from cryfield so I'm not really sure how lively it is. A couple of my friends live in Westwood, it is quite an effort to get to campus (if you're likely to be at gibbet hill all the time don't pick it!) but the blocks are really sociable because there is around 20 people to a kitchen and each block has a massive common room. However, all I would say is that your halls are what you make it, I know people in tocil, which is flats, but I'd say that their block is more mixed that my JM block. Go for the ones you like best and be really clear about what you want on your personal statement. Even if you don't get exactly what you want, you will have friends who live in other places so you can just spend time with them instead.
Just realised quite how long this post is so I hope its helpful!!