The most important thing to do is visit the universities you’re considering, ideally on one of their open days. You don’t want to arrive in Oxford as a proud undergraduate, only to discover that the Harry Potter vibe is grating rather than charming, or in London to learn that the bustle of the city overwhelms you. What’s more, visiting affords you the chance to speak to current students about their experiences. A five-minute chat with an undergraduate can be more illuminating than any prospectus or league table.
Along those lines, it’s also vital to consider logistics. You won’t just be choosing a university; you’ll be choosing a place to live for several of the most formative years of your life. Make sure you can take part in your preferred hobbies and sports locally; that there are shops and restaurants where you can find the things you like to eat. Also consider how tricky it will be to return home for the holidays.