In my amazing task of searching a english school in London I found many schools with a revolutionary method, the CALLAN METHOD which says: learn english in a quarter of time needed to do it with a traditional method.
From the beggining, it sounds like Maurer's method (famous in spanish radio stations with its commercial): english with one thousand words, but this method is much more than Mr. Maurer's method.
There are 12 differents levels and each level has its own book (10 pounds each book). Before starting the course you have to do an exam in order to see your english level and depending on it you will be placed in one level or another.
I went to a very good academy in Neal Street (Covent Garden, or Tottenham court road underground station). I like this academy because of their wonderful teachers and the atmosphere. I found it while i was walking in the street and it's like a "family". The teachers make the classes funny and there aren't too many students per class. The name is ABC School of English.
Well... I went during two weeks, but now I decided to change because Callan Method definitively is not that I need. You can try it with 3 trial lessons, but in my opinion is not enough to know the method.
The recommendation is 10 hours per week. And the method consists on a teacher who is all the time speaking english making questions from the book and you must answer the question fast, if you can't do it, the teacher starts answering with you to avoid you thinking in your own language. That's basically Callan method, make you think in english.
After that the pupils have to read (from the book), aloud, by turn; and after that you will do a dictation. During the first hour (two hours each day) you do things from past lessons, and during the second hour you learn some new words.
I think that this is a very good method for begginers or people without a high level of english, actually I met a japanese girl who reached my english level (upper intermediate - advanced, level 10 of callan) in two years time only. Learning exclusively with this method.
On the other hand, if your english level is high... this method starts to fail, because the evolution is slow. But in any case, you will improve your speaking skills, your listening skills and your vocabulary if you chose this method.
If you are looking for a method in order to prepare yourself for FCE, CAE, etc. perhaps you should try another thing.