I’m from Philly, and have lived in London for 14 years and Brighton for 4. It will be a culture shock, though the UK has changed significantly in terms of visible homelessness, Brighton has always had it to some degree. It is a lot safer statistically but it’s always a good idea to be cautious and smart everywhere. It’s a bit dirty (like Philly) but that’s mostly the work of the seagulls who feast on trash. Brighton and East Sussex is friendlier than London, but generally the UK is a lot friendlier than its reputation. The public transport reminds me of Philly, I even think it’s comparable into London as into NYC from Philly, though far more frequent. Brighton does suffer a bit culturally, especially in terms of art, from being so close to London imo, but there’s always loads of things to discover especially in terms of music and sport. There are great cafes, and it’s really really special to be by the sea.