Requirements for a student visa

I know that right now obtaining a visa for Japan is virtually impossible. So I'm speaking in the timeframe of later this year or sometime next year.
I am considering studying in Japan for 2 - 4 years to obtain a degree. I am British, living in the UK. I've not been to university before, but I have completed 12 years of education in my country.
How much money would I need to have in savings to get a student visa?
I currently have £7300 in savings, which according to Google is about 1.1M‰~BI would have more than that if went to Japan later this year or next year. Probably about £10,000 - £12,000. Also, I would not require student housing as I would be living in my girlfriends apartment. She doesn't need me to pay rent or anything in the meantime. But I intend on working a part-time job whilst studying in Japan to help keep study payments up. On top of that, I have recently got my TEFL certificate so I can teach English online to get some extra money whilst in Japan.
My Japanese level is conversational, so I intend on learning on an English-speaking level and growing my Japanese further through immersion and making friends.
Besides the money, what else would I need?
Thank you.

Ifve seen numbers like 3 million yen bank balance certificate required to apply for a student visa through a Japanese language school, which often runs 2-year courses, so the amount you have in your mind might not be enough.
And obviously youfd need to be accepted into a university in Japan to be eligible for a student visa – are you planning on enrolling into one that runs English-only courses? Youfd need to select the one you want to go to (most universities in Japan go for 4 years for a bachelorfs degree) and look into their entrance requirements.

@AK
Thank you for your response. Yeah, I can somewhat speak Japanese, I'm studying it myself every day and talking with Japanese people often via Hellotalk. But in terms of being taught Japanese, I'm not ready for that yet. So I'm looking to study a BA degree (that should be 4 years at a university I think) in Japan where the lessons are taught in English.
It works out very well for me because I want to continue to develop my Japanese while obtaining a degree. But I've heard getting into a university in Japan is very competitive and of course, expensive.
Sorry if my original post was not very clear, I was writing it on my break time at work and I didn't have much time.
I'm not in a rush at all to join a university, so it's easy for me to save up my money and think about what I would like to apply for until then.

I was wondering if you need to have already obtained some kind of university qualification before joining a university in Japan. Do you perhaps know anything of this? I've read that if you want to study in Japan as a foreigner, you'll need at least 12 years of education in your home country. I've actually had 13 since I done an extra year at college, but as for university, I've never been there.

The 12 years of education starts from elementary school, so that is referring to completing senior high school. You donft need any college/uni education in order to enter a university in Japan.

Whether you want to study ginh English in Japan would depend on what you plan to do later – if you plan to find work in Japan and live in Japan, you gmighth want to consider attending a language school full-time first for a year or two, then enrolling in a Japanese university course taught ginh Japanese. Just a thought.

If you want to study ginh English in Japan, there are some universities that offer courses in English – please look them up and check their entrance requirements/examination process.