There are lots and lots of things you need to consider when you decide to come to the U.K. to study as an international student. The biggest chunk of the cost for you is going to be tuition fees, which can range from £12,000 to £20,000, depending on the location of the degree, whether it's an academic subject, whether it's a lab-based subject, which year of your degree you're in, and exactly the subject that you are doing.
On top of that, you're going to have roughly £9,000 living costs; these costs rise to about £13,000 if you are studying in one of the big cities like London, Oxford, Cambridge, or Edinburgh.
You need to consider your costs of traveling home, as not all universities will let you stay there over the holidays; in other words, you might be forced to go home for Christmas as your accommodation may be used for tourists during that time, so you will need to factor in the cost of traveling home three or four times a year. Communications with home might require you to get a more expensive mobile phone contract than other students. You might need to get calling card, or you might need to consider accommodation that has Wi-Fi included, as not all of them do.