I know people who go to Sussex and have graduated from there and I'm going there this year. You seriously cannot judge a place on the people, I learnt this from my own experience when I went to the better college thinking that I would never go to parties or anything like that because of the people being middle class and really into their work. I couldn't be more wrong, not only did my college have a massive range of people, I went to hundreds of parties. And Sussex is the same, yes there are hippies but not on all parts of the campus. There's a MASSIVE range of people, upper class, middle class, lower class, people who go out partying constantly, people who don't, people from all over the world. Sussex gathers a massive range of people because of its location, near two great cities.
But if you didn't connect with the university, that's your instinct telling you something's wrong. It sounds like you're only going there to party but you will get parties at all universities, whether they're in the middle of no where or in the middle of the city. Don't not go to a uni you like just because you think nobody will want to party. Are you kidding? It's university! Freshers ALWAYS party. And York university will be no different. Plus if you think you will be more dedicated to York, then go for it. You end up paying for it remember? And if you think you're going to put more effort in to get work experience and volunteering, and there's better societies, then what is stopping you? Every university has a diverse range of people (apart from Oxford or Cambridge to some extent). Just go with your instincts or prepare to be unhappy.