There is an enormous difference between being a qualified English teacher and doing an online TEFL, as I am sure you are aware, Martin. If you want to take your backpack and have a bit of an adventure, then there are plenty of places that will give unqualified people with an online TEFL some teaching hours. You may also be able to find some private tuition work. However, reputable academies and places such as the British council would want a properly qualified person. A CELTA is consiered to be a relevant qualification for ESL language school tutoring. (Many of my contacts in these places have MA in applied linguistics on top of a bachelor's degree, and other qualifications.) As for becoming a teacher in an English medium international school, you will need a First Degree, either a B.Ed or PGCE with QTS and, for reputable schools, at least two years successful teaching experience under your belt, just to be shortlisted.