I've read a lot of posts on this forum warning people against coming to BA to teach English, but I wanted to offer a few words of encouragement. I've been here for almost three months, and I've had an excellent experience so far. For people who come here with no training or experience and expect to find a job teaching English, it is probably very difficult, but with a TEFL certificate you shouldn't have any problems. I had about a year of experience teaching English in the States before coming here, and I've had plenty of job offers.
As for the cost of living, it is more expensive than many people realize before arriving here, but you can certainly live on a teacher's salary. You should know that institutes pay monthly, so it's a good idea to have a few thousand dollars in the bank to get yourself started, but you don't need to have enough savings to support yourself for the entire duration of your stay. You won't make enough money to support a lavish lifestyle, but you certainly won't starve. As long as you're willing to live somewhat frugally and work hard for your salary (that's part of the experience, right?), you should be completely fine. Feel free to contact me for more information!