Where to learn English? It is very difficult to answer this question, as there are plenty of courses: how do you meet the right one that suits your needs?
After reading English levels and How to choose a course, you should be able to have a general idea, but time is limited and you would need to visit a lot of schools of language, universities and teachers to decide.
ENGLISH IN LONDON can help you choose a good course: their previous experience is very important, as allows you to avoid a lot of mistakes, and at the same time, to get better results with the same effort, or the same result with less effort. They personally know and have agreements with qualified schools of languages and good private teachers that allow you to attend English courses at discounted fees.