If you want to go into adult education, there is a specialist PGCE for this category, but it won't allow you to teach younger age groups, whereas with a secondary PGCE you can use it to get into adult teaching (although the two are very different). Ideally, for the post-16/post compulsory route, you would be wise to have a degree in - or related to - the subject you want to teach, although it isn't always necessary. You should, however, have a good grounding in your teaching subject.
When I did my (post-16) PGCE ten years ago, it was part time over two years and involved having a teaching placement for the duration. The written work was largely reflective based on our placements, and we had to have mentors and regular assessments by our course tutors. The course was non-subject specific - people doing the course were teaching everything from martial arts to gardening, from dance to ESOL. It made for a very good mix.