Not an English teacher, but your questions could apply to any teacher.
When you do your PGCE, you should peak at around a 50% timetable - meaning you have as many frees as you have teaching time. You will probably find that you still need to do a bit of work in your own time because all your lessons have to be fairly flashy and well researched.
As an NQT, you will probably have around a 75% timetable, including time to meet with your mentor. As an English teacher, your marking load will be high - you have to read carefully all the homework, whereas in a subject like mine, you can get away with skimming for keywords if you are up against it. Some of your lessons will be fairly easy planning-wise - reading lessons being the easiest (students do their own private reading, and you have them come up to you to read aloud for 5 minutes at a time). Similarly, if students are composing their own essays or poems, you can have an 'easy' lesson. You might even be able to get some of your own stuff done, but this is never a guarantee.
How teachers manage their non-contact time is very personal. I tend to mark at school, and do planning at home, but I am pretty much an exception in my school. I can't bear the thoughts of taking books home and them disappearing into the chaoes of this household - 'the dog ate it' takes on a new meaning.
Teenagers are a mixed bag. There are some that are lovely and that you really click with, and there are some that are horrid. You get plenty of 'Laurens' (ie Catherine Tate). I found working in state schools with 30 6-footers in a class really hard work. It is very stressful - not necessarily in an unpleasant way, but you are always on your guard and working at 100%. I work in an independent girls school now and it is very pleasant