I am a first year at Leeds uni and I am loving it! There are loads of opportunities to make friends, especially during freshers and in societies, where you share the same interests. There are snobbish people but that can be easy to avoid. Regarding safety, the campus itself is totally safe. There is security roaming around all the time in their vans, as well as the little huts they have. I have also walked round campus on my own late at night felt totally safe. The safety in the city really depends on where you go. Personally I feel safe in the city centre and will happily go alone; however it does feel a bit dodgey by the river and train station, however this is somewhat out the way.The socialness of your flat will totally depend on the people and whether they are the party type or not. And of course the price of the halls really depends on which one you apply for. The cheapest I believe is £85 per week which is Oxley. However, this is located in Headingly and is about a 20 min bus ride so wouldn't reccomend. Henry Price is very reasonable at £112-125 per week (depending if you have the en suite or not) and is self catered and is located on campus. (Perfect for those who like a lie in!). On the more expensive side is Cityside and Central village which are more modern buildings and are going for around £135 per week. And then the most expensive are those which are catered such as Charles Morris.
Hope this helped, and congrats for your offer x