Hello there Chloe,
I currently teach this, and we are nearing the end of the first course. Basically below Entry 3 level you are reccommended the course, though your command of english is pretty good and I would go for the test.
The course is ESOL with government citizenship materials, and ours lasts for a year. On that course you need to progress from one ESOL level to a higher one. The college will also give you a certificate stating that you have completed the above course.
Regarding fees, the courses have been free this year, but next year, most will charge. You will also have to attend the course regularly.
Good luck!
Caroline