I completed the PGCE last year, applied for my current job in Feb. As you said, people at my university were surprised a job came up so soon. But many schools want to sort out their next academic year ASAP.
Questions to ask about the job itself:
How has the vacancy arisen?
Someone leaving? Why? Career progression or problem? Dept expanding?
You may get lucky and get an honest answer here!!
What are the staff turn over rates? Everyone leaves jobs, but a higher than average turn over rate may be cause for alarm.
When I went for my interview, it was the first post I was interested in, long way from home, so went with a very open mind, with the need for the school to sell the job to me. Seems arrogant, but I wanted to be sure.
Interview day...
Meeting with head, chat with them and other candidates. Other candidates felt the need to compete with me asking questions, I left them to it, asked questions only when I thought the head could expand on her school info / talk.
Tour of school, don't forget, you need to be switched on for the whole day. If a kid shows you around, the head could be talking to them after, asking them about you. Remember this when you turn up at reception, be polite!
In Deptartment, chatting to ICT teachers, while other candidates teach a lesson. I asked lots of questions about resources, work, CPD, that sort of thing. Didn't want to be coming into a dept with no prior work or sharing of files.
My lesson, had to teach a lesson infront of HoD.
Lunch, then formal interview.
Few things, don't offer the world if you can't deliver it. You will probably be asked about extra curricular activities you could offer the school, be honest but don't say something you may regret. They will remember and remind you in Sept!
Be yourself, obvious, don't feel you have to ask questions, ask when you feel you want to know something. I asked about parent involvement, and how diverse the area is, only as the impression was a lot different.
Good luck.