I have taught English for many years and in many places.
As well as private students, I currently teach groups of teenagers and adults at an academy in south London that teaches courses in Business, Catering and Hospitality to foreign students.
Fehmi Hanoglu, Deputy Pricipal, Docklands Academy London
I have given free English classes to adults recently arrived in the UK at a refugee support centre and to professionals, some of whom spent a period of time in London primarily to improve their English skills.
I've worked in various kinds of "classrooms", from slick college lecture rooms, to schools, to student's homes and offices. For some busy London professionals I've even given classes at cafe tables amongst the coffee cups .
It's lovely to have access to audio-visual equipment and other facilities, but the heart of an effective and enjoyable language class in any context is materials that suits the needs of the student. This includes ...
The time a student has available for learning English.
The skills base on which the course must be built (ie. how much English the student already has)*
The student's particular interests.
* The advantage of taking a series of private lessons is that, if you have previously studied English elsewhere, there's no risk you'll end up studying the same material and making no progress. I WILL DESIGN THE LESSONS SPECIFICALLY TO YOUR NEEDS.