Language school in Tokyo

Hello.
I am from England and next year I plan to attend a language school in Tokyo. I have researched a few and so far the ARC language school and System Toyo Gaigo has really caught my interest.
I only know kana at the moment and I find it hard to self study.

Also I haven't checked this out yet, but I intend to start with a 3month course on a tourist VISA. If I am loving it and want to carry on is it possible to get a student VISA in Japan before the 3 months is over, so I can carry on my studies? I know I should just ask the school but hey... why not ask you guys right :)
Thank you very much.

I doubt that you could get a student visa with less than 3 months notice. I'm currently applying for a place at a Japanese school, and they require 4 months notice if you require a student visa. If you made a decision about extending your course after 2 months, you could try to get your tourist visa extended to 6 months, which should give you enough time to apply for a student visa.