Please contact one of the language centres, which are now literally at each University. Training in such centers is usually done via the common school methodology: the study of grammar, memorization of vocabulary, practice pronunciation, composing dialogues, listening. Classes, thus, nothing, in principle, no different from the usual school (the only difference is that the training centers are not free): questioning, explaining new topics, exercises its consolidation, homework. However, the knowledge gained in such centres (as well as long term courses or in specialized language schools for adults) remain very stable for many years.
If you are interested in not the actual mastery of language, but only some region (e.g. business English), visit one of the online sites that supports such a course, or do individual training with a teacher. Unfortunately, the level of proficiency in English, in this case almost completely will not depend on the diligence of the student, or talent of the teacher and the amount spent funding. In General, the cost of the most expensive such courses will include the price of textbooks issued directly to the UK or, at least, in the US, conducting master classes of leading professors of the foreign business centers (online at the Internet and in live communication), payment for familiarization tours.
If the limit of your dreams – learn spoken English then here we have several training options: courses, learning which involves the development of special communication methods;- courses and training which are conducted by the lecturers from the UK and the US (by different methods);- short courses (1 to 6 months), training which focuses on mastering the basics of the language that can be useful is that in a tourist trip for utilitarian communication with the seller of the Souvenirs, or a taxi driver.
Go for training or for permanent residence in target language country (UK, USA or even New Zealand, if you want). A couple of years of classes, even the highly qualified teacher you, of course, is not enough. Not enough, perhaps, of a lifetime to thoroughly learn the language, the carrier of which you were not born (or at least through adolescence). However, live communication with those for whom English is their native language, and a deep comprehension of the mentality of the people of these countries will lead, eventually, to the fact that you will be able to get closer to perfection in the mastering of this language. But remember that no wonder they say: where was born there and handy.