I'm living in dean's hall now. It's moderately expensive. Dean's hall is a central location right next to the city center. You won't have to pay for taxi's on nights out. It's just under a ten minute walk from main campus. The rooms are fairly nice. Very big desks and the couches are comfy enough. Flood waters reached close enough to dean's hall in the last couple of years, but no rooms where flooded. Most people in dean's hall are first years
Castlewhite is more expensive, but is right next to main campus and is only a couple of minutes from the Western gateway building. The rooms aren't as nice with less comfortable furniture. I think castlewhite has a more balanced mix of years. Flooding is a distinct risk.
Which is more convenient for college depends on what course you want to do, (which buildings you'll be going to). Regardless of college, dean's hall is more convenient for night's out/ shopping while castlewhite is more convenient for going to the mardyke and main campus
Straight Up Funk:
Know exactly what you mean
Send Lancaster hall off washington street an email, explaining that you want to live with mature and quiet people, and ask whether or not it would suit you. They normally only take 3rd/4th years and postgrads, but if you ask, they'll probably accommodate you. They seem reasonable enough. If you want to live with other second years, then copley court might be worth trying, but keep in mind location when you book a place. Arcadia hall is probably quiet enough, but I can't be sure.
Lancaster is quite nice. I'm thinking of living there myself next year
It's not too expensive if you go for the cheaper rooms. Copley is the cheapest of the lot, but the quality of the apartments isn't great. It's a quiet enough place even with the mix of years there.
Again, the best accommodation for you to book depends partially on which course you are doing.