Hello!
Firstly - don't worry too much. The university has a range of options to help people out who are in real financial need, and do consider each person on a case by case basis. You wont be excluded from university because of lack of funds.
College accommodation is expensive. The university justify this by making the valid point colleges offer a lot more than just a place to live - they are actual communities and the college system in general is great. However, there has been a lot of concern over rising fees and it even hit the national news. BUT there are ongoing student led campaigns and protests about the cost, so hopefully the university will be forced to remedy the situation. Watch this space! :P
But... don't worry too much. Whilst college is expensive, almost everyone lives in privately rented accommodation after first year (the university actively encourage it, and can only house a limited number of non first years anyway). There is a massive range in prices for housing, however if you are prepared to live slightly further out (or find a really good deal) you can find rents of around £60 per person per week, with a 25 min walk to lectures (or if you have a bike it's really handy whilst still being a cheap way of getting around!). Adding bills and day to day costs like food, toiletries etc. I have been able to live every year for under 4-5k, which fits into my loan/ grant comfortably.
Living in college is only for one year, and is really worth it. I had to use my savings to make up the difference, however in every other year my costs have been covered. Also, while they don't recommend you have a job during term time, some people do. It depends what degree you do and how many hours you need to work. I personally couldn't keep up a job during term time however getting a summer job is a good option and if you live at home rent free during summer you can easily save a lot over the break!
Durham is a great uni. It has a great academic reputation. Also don't worry about not fitting in - people at Durham come from all backgrounds. Durham has a reputation for being posh, and there are some rich people here, however the vast majority are very normal!