OP, one very important thing you should take away from this thread before you get on that plane to Boston is that a statement such as “I do not really like the American way of life” which might be considered a reasonable statement of preference in most parts of Europe might be considered surprisingly rude in the US. It’s something continental Europeans Iike us (as I assume you are from continental Europe, not the UK) from rather blunt cultures which are perfectly happy sharing their opinions, positive or not, of any culture in the world, including their own, I need to learn so they won’t put their foot in it when it matters.
I am assuming you are eligible for EU fees as opposed to international fees in the UK, so financial considerations should really play a large role I your decision. Tufts is need aware for international students - can you afford all four years there, including air fare? How much more will you have to pay compared to three years in the UK? Is it worth it?
If you are worried about how far away the US is and that you might not feel comfortable with the American way of life, starting out your academic career in the university best suited to your interests in the UK might be a good compromise (again, I am assuming that you are not actually in the UK now. There’s always grad school in the US. If spending four years in Boston would not make you happy, don’t go!
Note though that the UCAS deadline is Jan 15th. Unless you have already final grades for your final year from the school you attend, you will only get a conditional offer until those finals are done. Until then, Tufts (assuming you can afford it) should be considered your safety anyway.