I did the GTP 2 years ago. I found it really handy, because I had been teaching for quite a few years without a PGCE, but wanted to get a professional teaching qualification without the fuss of going back into full time study.
I don't know what you've been told about it, but the time scale can be anything from 1 to 3 terms in length depending on your previous experience. I know that places were hard to come by and preference was given to 'shortage subjects' but it was hoped that more places were going to be made available in time.
The course is almost made to suit each student and basically comprises of gathering evidence to show you meet the criteria ( bit like an NVQ really). Unfortunately, you also have to do a major assignment for each term you do it over and also go to a different school from the one you have attached yourself to for a few weeks to broaden your experience.
If I remember when I did it my 1st port of call was the Dfee (maybe try their website) who told me which Universities offered the GTP in my subject, and getting my headmaster to agree to me doing it. I don't know, but maybe that's where our situations would vary? If you don't already teach you'll have to get a school to agree to take you on. That may be easier than you think, as some schools will see it as cheap labour.
As i said, it's a handy way of getting your professional status. However, don't expect it to be a breeze. As I was also teaching a full timetable at the time it was a bit like doing 2 jobs.