Becoming a teacher of adults is less rigorous than entry into full time school teaching. Many providers of adult courses will assess you on your experience. However you will be expected to do additional training courses if you have no proven experience of training other adults, and you will be expected to join the IFL.
There is often a kind of running open advert for adult tutors at local colleges, so try having a look into this.
In addition many councils run community-based learning schemes through which you could pick up part time / occasional work without giving up your day job.