I'm a TEFL teacher, so I think I can help.
First, lack of a degree won't hinder you, as long as you have a CELTA or a Trinity CertTESOL. Don't waste money on anything else, they won't be recognised in the UK. The course should be either 4 weeks full time or 9 months part time and should cost in the neighbourhood of £1000. The fee is the same regardless of how long you've lived here.
Second, EFL teaching is a job people do because they love it, not because it's a great living. It's not. You most likely won't have work from November to March unless you go abroad, and even if you did find a year-round gig in the UK, it will never pay more than maybe £1200 per month. I had a full-time, year-round job, and I left it because the working conditions were so dire. I loved the work itself and my colleagues, but I couldn't handle being treated so badly. Not every school is like the one I worked for, but the best ones are very competitive. Also, if you don't live in London, Bournemouth, Brighton, Edinburgh, Leeds, Bristol, Oxford, or Cambridge, you most likely won't find work except perhaps in the summer.
Having said all the bad stuff, I love my work and wouldn't do anything else. It can be a very rewarding career, and such a great opportunity to meet people from all over the world, and the other teachers will be great too.
If you have any further questions, feel free to send me a PM.