The i to i online course is a perfectly adequate qualification for most TEFL jobs abroad. The exceptions are some Universities that will require a degree in English Language or related subjects.
As far as teaching English in a language school in the U.K.though, it is of no use at all. You say "a few schools etc. in my area". What kind of schools etc? I'm guessing privately run language schools teaching English as a foreign language.These schools are very tightly regulated in the U.K. the reason being that almost everyone in the U.K speaks English as their first language, and a lot of them will have studied English at school to at least standard if not higher grade, and without regulation anyone could set up a language school and teach English to foreigners. As I'm sure you can imagine, that would lead to a very wide range of standards of teaching from good to very poor indeed.
There is also the competition factor. Europe is one of the most popular places amongst TEFL teachers. This is because it is not so far to travel for Americans and Europeans, and the culture is not as alien as it is in Asia and Africa for instance. The standard of living is higher, and it can be easier for native English speakers to get by without having to learn the local language. For those reasons the competition for jobs in Europe is much higher, and so the level of qualification needed is much higher. Often the entry level is a CELTA certificate and sometimes a relevant bachelors degree as well.
As I said before, the i to i certificate is perfectly acceptable in most Asian and African countries, as well as South America. Indeed it is the qualification I have. It is not as good as the CELTA course though, which is up to ten times more expensive, is a two week full time course, and involves a lot of hands on teaching experience. You don't mention why you don't want to teach abroad just yet, but let's face it, for most people the whole point of doing TEFL is as much about travelling and experiencing the culture of other countries as it is about teaching English. If your more passionate about teaching English than travelling, you would be much better off going to university and getting a degree.
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