I've just got a place on the primary GTP. I have approx 10 years experience in an IT environment, which sometimes involved training adults but that was as close as I got to teaching. I also did a small amount of IT work for a few local schools. I did 2 weeks voluntary in Dec 2010 just to make sure teaching was what I wanted, then I started to put things in place ready. I then started again with the voluntary work in Sept 2011 working 2 days per week across a range of year groups. In October I was asked to cover another TA officially for half a day a week (paid). My interview was in January, on the day of my interview a TA had suddenly left at the school and I was asked if I could take over that role full time until the summer holidays. So was able to add that I would be working full time as a TA until the summer holidays. I would recommend as much experience as possible though as there is so much to learn in 1 year with the GTP - you do have enough time though to get enough experience in but you may have to get some time off from work to be able to do it.