Japan has a small number of Universities where the classes are taught in English with all other universities being taught completely in Japanese. If you want to go to a regular Japanese university, you need to have roughly the equivalent of 1.5 - 2 years of study at an intensive Japanese language school (5 days a week, 4 hours a day) just to pass the entrance examination for those schools.
You can complete a degree full time in Japan in English if you desire but it's going to cost you a lot of money - anywhere from $6,000 to $20,000 USD per year. You'll either need a lot of savings, generous relatives, or scholarships, loans, and grants.
Here's a list of universities in Japan that teach classes in English:
International Christian University -
ICU International Christian University | About ICU | Finance | Expenses
Waseda University -
WASEDA UNIVERSITY- Tuition And Fees -
Sophia University -
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Temple University Japan -
Tuition and Fees - Undergraduate Program
Ritsumeikan Asia Pacific University -
Admissions International - Finance Info
Of course, if you want to live in Japan long-time, it's advisable to complete a 4-year degree somewhere so that you can later get a work visa. In my opinion it would be far easier and less expensive to do this back home in England. But it's not impossible to do in Japan.
If you just want to spend a year in Japan learning the language then return back to your country, then just come on over and join a Japanese language school.
I have no idea what the best language schools are as I've only ever been to one. I'm currently at the Academy of Language Arts in Iidabashi, Tokyo. It's decent enough for me. Here's a list of language schools. It's up to you to research and figure out which one would best suit your needs, goals, finances, and learning styles:
Japanese Language School Guide
School Search : Japan - Japanese Language Schools