Hello there, just read the above comments and wanted to weigh in on a few things to give you a rounded viewpoint.
I'm currently on the Teach First LDP and it's not as horrific as the above comments make out...you get 6 weeks training across summer and start at your school in September. You're on a reduced hours timetable and receive an awful lot of support so I wouldn't worry about it from that point of view.
You do have a large workload, as you're teaching, marking and planning as well as researching and writing your assignments. From what I gather though, there is a lot of work involved in a normal PGCE course as well, including written evaluations of all your lessons I've heard, which as a Teach Firster you won't have to do. So far I've found the hands-on experience absolutely wonderful and I think a baptism of fire is a great way to learn. I guess this depends on your learning style.
I spoke to a friend recently who did a Cambridge PGCE and she said she felt like she mainly had a qualification in form-filling. I can guarantee you that the LDP doesn't feel like that. You're in the classroom, every day, actually interacting with this kids and not just going through bureaucratic procedures.
Re: Teach First only being in cities this is broadly true, however I'm in the East of England and the coastal town placements here are just as deprived as the inner city schools in, say, London. The children face very different problems, but there is still a lot of good work to be done here. On TF you really do feel like you're part of something very exciting, and all the hard work seems like it's for something very special.
I would also like to say that not everyone who does the LDP is in it for solely 2 years; there are some people who do it, including myself, who genuinely want to make a difference, and wanted to go into teaching in a slightly different route from the norm. But like I said, it's a personal choice. You need to think about why you want to teach in the first place - does it fall in line with the charity's vision?
Hope this helps,
Emma