"I haven't got a degree and I am seriously thinking about getting one."

I would always encourage people to continue learning whether this is through formal courses or extensive reading. There's plenty of evidence to show that those with a degree generally tend to earn more over lifetime than those without a degree. However, many of the trades for which a technical training is often needed, seem to do better in terms of salaries over a lifetime - plumbers, electricians, builders etc. Of course there are always exceptions - individuals who pursued an idea or an innovation, and in some cases dropped out of university and went on to become millionaires.

"I am currently in London,looking for colleges and universities which run teaching development courses and degrees, preferably 2 years long,..."

I may be wrong but I have not come across any 2 year degrees in the UK, unless you are thinking about what used to be called "Associate Degrees" in the USA. Tuition fees will go up in the UK and you will be looking at finding £9,000 a year. This is putting some young people off studying for a degree and being saddled with years of debt.

"...in subjects different from efl."

This is difficult because we know little of your background. Before choosing a 3-year degree progamme in the UK, students will take a number of subjects at advanced level between the ages of 16-18. Often their degree choice is determined by the subjects they studied at secondary school. So my advice if you want to to do a degree is to think carefully of the subjects you did well in at school and see if this aids your choice of an undergraduate course. For further information you could Google, " Teacher training courses in London." There are also schemes for mature students. Personally, if I was to do it all again I would try Scotland, as many universities are considering whether they charge the £9,000 a year.