For those who are thinking of studying in the UK I would highly recommend it to everyone! This is a once in a lifetime opportunity so take it! Explore as much as possible when you are here and do more than just study. If possible, speak to an existing student at the university and attend as many education fairs in your home country to help prepare you for the UK.
In Japan, humility is more valued but outside Japan, confidence is more highly valued and so I have changed to adapt to my new environment. In the UK there is more emphasis on group learning whereas in Japan, it is mostly based on lectures.
I would also recommend that you study as much English language as possible before coming because you are expected to contribute to the discussion with native speakers from day one on the MBA. Finally, I would suggest you increase your familiarity with accounting as I have seen many MBA students struggling with the accounting exam which normally happens in the first term.